nipper

It's time to give it to a real shop, pay them for thier opinion, as it can be quite a few things at this point non good.

Sometimes you have to wait for the noise to get worse. You dont have a broken suspension spring do you? They arent always obvious, rare on Soobys but do happen.

Show and tell, what are we looking at, pick one http://i567.photobucket.com/albums/ss120/jacksonMS30/SparkPlugReading_zps9f2f50dc.jpg

Or the engine is running

How old were the plugs?

Sure, the ONE TIME, the ONE LOUSY TIME i dont suggest moving tires, its the tires.

ABS is a flow through mechanisim, meaning brakes work without it. An early abs like this would bleed off pressure, not impeed it. Smoking brakes, frozen caliper and you boiled the brake fluid.

Do you have the factory sub-woofer?

If your alternator is wonky it will affect the digi gauge reading.

CHeck the 3rd brake light and the pass through boot (wires) at the top of the tailgate.

I wouldnt bother swapping tires, but I would have the entire front end inspected for wear. Also check the Transmission mount and drive shaft.

Dirt in the carb, time for a rebuild?

Are there any markings on yours? All it is is a solenoid with a needle valve. Why do you think yours is bad? Nissan or datsun part will work

Choke, or a stuck float by a little dirt. Or gnomes.

lso be a bad electrical connection

Is it possible, long shot here, a fuel line is rusted or near pinched and the sheer act of DARING to remove a flat tire (the other 80% is perfectly round, a waste) and something is pinching a line?

Yes research is hard. We shall just wait for somone with more knowledge to show up. I shall sit here and thumb through the FSM for light reading.

A little groaning is normal in a Subaru as the computer figures things out. The only time I had one not do this it was a manual

Ok so I take back my unloved comment

Wow so many places to start This car needs a proper tuneup. Plugs Subaru wires fuel filter air filter. I et you have some bad plugs. PCV valve too. Next your due for a timing belt, like it of not, with a water pump cam seals idler and tensioner. Then trace down the FRONT O2 sensor. Hell at this poin replace one then the other. Normally not my suggestion but the car hasnt been maintained all that well and thats coming home to roost.

Or a simple vacuum gauge will tell you if the cat is clogged.

Eastern brands are the cheapest and junkiest. How many miles? It may just need an O2 sensor and a tuneup. Dont jump to expensive conclusions as cats dont usually fail on these cars.

The sensors may just be eroded. Inspect them they should be little perfect cylinders. Cleaning may help. Inspect te tone rings but usually it takes something to upset them.

If you bled the system by pumping the brakes, you may have damaged tired seals in the master cylinder and are burning brake fluid. Check the line to the booster is it wet?

To be honest when my unit went bad I had the dealer rebuild it to get it right. Transmission shops are shady at best. Its not hard to rebuild yourself I just dont have a garage, nor at the time a paved driveway. If the tranny works, I would just replace the unit. Since it sort of hangs on the tail of the tranny, it can always be used on another tranny.