My brother owns a 2003 Eclipse GTS 5 Speed. He's in college and it sits except for me occansionally driving it. It runs well but has a couple issues that I myself and 1 or two shops haven't been able to diag. I want to bring it into my garage and do a couple things, but thought I'd get some advice from people who regularly work on Mitsubishis as I've worked primarily on Hondas and Toyotas. The eclipse is a lot of fun although does have a tendency to eat axles.

Problem 1:
The car fires up great, but sometimes has a tendency to die. Coming off the highway it will die if you clutch in and coast. Originally thought EGR solenoid so It was replaced it but issue persists. It also died once at idle during a carwash. It has always fired right back up.

Problem 2:
It also smokes in the rear part of the engine after awhile, I haven't been under the car as its fairly low and haven't got it in my garage, but it is a considerable amount.

Once I get it in the garage I'm going to pull the Plenum replace both valve cover seals(the smoke could be from the rear valve cover leaking on the exhaust), the rear spark plugs as the fronts have been done. Curious if a O2 sensor could be a culprit for it dying, although no check lights which I figured it would throw codes if O2 was a issue. Anything else I should run through with the Plenum off? I want to cover all my bases and try to snuff the issue out, so I don't have it all back together with the same issues.

Anyway thank you guys for any help you can give me and also for reading. He loves his eclipse, but its been sitting for a year without regular driving and I want to give him his car back hopefully fixed. Until I have to replace the clutch because the throwout is noisy. XD