1 Lucky Texan

if there's noise/symptom there now that absolutely wasn't there before - and given the trip you are planning, the risk of a major headache on the road in this car as it is now is WAY to high. Valves can easily burn/erode if they are leaking. the key would be a GOOD diagnosis before anything else, but, be prepared for bad news and get Plan B set-up NOW. time to call-in any favors or get some help from family, etc.

don't drive with a donut spare without using the FWD fuse. all 4 tires NEED to be identical - same brand/model/size and near each other in wear. maybe the tires you bought are asymmetrical and one got mounted incorrectly?

^^^ good Idea Citrasolv might work, and, actually, WD-40 is a decent solvent, much better than its lubrication ability really. Alcohol could work but would need to be tested. I would test w'ever you use on some 'hidden' plastic first. Check for any 'gumminess' after use and clean-up. Be prepared to follow-up with some cleanser as most of these will have an odor.

calipers can bind intermittently, often due to rubber sleeves on the slider - they swell up sometimes. many folks remove them. extremely rare but abd hydraulic hoses have been known to hold pressure. check wheel movement for bad wheel bearing i guess? basically, if the noise is in sync with tire rotation,that tells you which parts to examine. And, if it is noisy at walking speed, pace the car while someone drives slowly to determine which side the problem is on. after a highway run, an infrared thermometer might fine a hot hub - stuck caliper of bad bearing might cause more heat. any wrecks or work done to the car before this began?

I have no help other than to suggest you are not far from Shawn at RetroRoo. Founder of this Forum where we are writing! https://www.retroroo.com/

there is a youtube video of an inner (front) DOJ being regreased and rebooted in-car. Looks awkward but do-able.

loose sway bar endlink?

not as cheap as DIY I'm sure, but user traildogck makes some trans and motor mounts and some other bushings. I think he sells thru ebay. ?? paging @traildogck

the little parking brake shoes/gear inside the rear rotor might be making some noise.

Daniel Stern may still have a website devoted to auto headlights. I have seen one type of LED aftermarket that had a cone on which the led was 'back firing', seemed to be trying to duplicate a properly oriented line source.....? And, some I think have set screws so you can rotate them to try to create a good cut-off line. Dumping the heat is yet another problem for some folks. There's a little fan or some heatsink - some flexible - that sometimes requires deleting or modifying any rear cover on the light assembly Morimoto or other HID projector upgrades are often considered better than LED.. if any position on the car uses 9005 or 9006 bulbs, there's a 'hack' allowing use of HIR bulbs (Toshiba?) 9011 and 9012 - supposedly about 20% brighter. Just filing a tab down so the bulb will bayonet into the holder. there may be some good youtube video comparisons on this subject.

I second the addition of auxiliary lights. LEDs in a reflector designed for a filament will splatter all over the place.

I suppose the 'intensity' 'could' decrease with use of the FWD fuse, however, all the same parts will be turning at the same speeds.

maybe you'll get lucky and could hear the leak? perhaps get some tube of some type to 'sweep' all the joints and the condeser , etc.

timing likely slipped. less likely, stuck or broken valve. find a diagram/pics on-line for your engine, bring the crank around to the timing belt install mark, check the cams' timing - double check with a tooth count, also found on-line.

check the seal on the gas cap for tears/cracks.

I think the most common source of P0440 on older soobs is rusted-thru holes in the tank filler neck. have to look behind the plastic usually. But, if the car has always been in Abq, rust seems less likely than something like a cracked evap hose or cracked carbon canister, etc. bad knock sensor will kill power, might lead to knock noise, and often won't throw a code. This is one sensor where a cheap ebay unit has worked well for folks. on the braking....maybe look for loose sway bar endlinks?????

any sound at all? I have read that carrier bearings on the DS can really howl - dunno if they can cause vibration with no noise.

dburton - you DO run high octane fuel as suggested in the manual right?

you might check over at www.nasioc.com - those guys really appreciate you doing some searching and reading before you post though. that said, a beefier rear sway bar will not affect ride in a straight line, but will keep the car flatter in turns. easy and not crazy expensive.

if this is something you only notice when highway passing (above 70mph or so) then yes, try the batt disconnect reset. I ALWAYS do this before a 'road trip' with our 03. It helps with trans 'flare' when passing at high speeds. the tps is how the trans knows a demand for acceleration has been made. some folks have found use of Trans-X to help with slow engagement - but that is not the same as downshifting really.

OK, does it 'seem' like it is in sync with tire rotation speed - or could it be about 4 times faster, that would be ~ driveshaft speed. could you have a helper pace your car with another car , perhaps with a 3rd person as observer, on a 2 lane road such that any bouncing of a wheel might be observed?

yeah, that's why I said 'about' - it has to do with mass ratios plus, typical 'one-driven-axle' cars lose 'about' 13% (IIRC) thru frictional losses but I have read AWD is about 20%...as you said, complicated. his car may be closer to 15-20:1, some higher power cars may be closer to that 9:1 .... I guess someone could measure their accel before a mod like lighter rims, then after - but the numbers would only be good for identical models..... or, take an accel measurement now, then put a coupla 50lb bags of quikcrete in the car, make some new runs and compare. and of course, doens't really 'add' hp, just reduces a 'parasitic' loss of hp. maybe there's a site where values can be plugged in?

reducing mass frees-up a pony or 2 for acceleration. lighter rims, maybe a lightweight crank pulley, if you are always near home and help is easy to get - leave the spare and jack at home. Don't haul around any excess gear. If you literally never have passengers, take the seats out. you can make the car more fun to throw around the corners, cops rarely care how fast you take a legal turn. stiffer springs, fresh struts, maybe stiffer rear sway bar and stickier tires, good brakes, etc. 9-11 pounds weight = about 1hp, 4 pounds rotating mass = about 1hp.

easy for confusion to happen so, be sure to get IMpreza-chassis parts and not legacy Outback stuff. use the VIN if possible. many folks have received wrong parts due to the whole 'outback' part of the model's name.

well, you might avoid NASIOC......