Just had the y-pipe heading to the catalytic converter replaced last week, and the car had been running and sounding great. Took it on a 2,000 mile road trip, and all of a sudden as we're getting home the car is idling really rough, not turning on well, and the oil pressure has dropped. It also sounds like it did pre y-pipe replacement. Any initial thoughts? Obviously an oil leak seems likely, but I just wanted to see if all of these symptoms could be related to that, or if there's something else going on.

Inspect the spark plugs and/or remove plug wires one at a time to find the dead cylinder.

Thanks I'll check for that

Well new symptom - big oil leak. Ran it for a bit today, started fine, but about an hour after I turned it off it had a nice big oil stain on the ground underneath it.

Could all of these issues be related to an oil leak/gasket problem as opposed to something bigger? The mechanic I talked to earlier said he thought it could be a bearing problem, in which case I might as well just start thinking about an EJ22 swap... lol

The running crummy and hard starting are not likely related to oil in any way. An engine will start and run fine with no oil. It just won't last very long...

 

Check for intake and exhaust blockage, fuel deliveey, spark, timing, etc.