I have a 2001 rs with aftermarket intake, headers, cat and exhaust. It has around 105,000 on it, and I'm noticing it's not nearly as quick as it was. There's nothing wrong with it, it's not pinging or lagging, there aren't any weird sounds or misfire codes or anything, it's just not what it once was.

I'm tempted to do some kind of engine cleaning (I've heard that Marvel Mystery Oil or Seafoam are good for this), but I'm interested in others' experiences or thoughts on this. Bear in mind that this is my driving car, and I would rather have it a little slow than broken.

Is it worth doing? If so, what's the best method?

 

seafoam through the intake is always fun...get along peice of vaccume hose, find a vaccume line from the intake manifold, have someone get inside, start it up. hold it @ 3K rpm till about 1/4-1/2 the can is gone. shut it off, let it sit for 15 minutes...start it back up and smoke everyone out!!!

 

Riiiight. Re-read the "slow is better than broken" part of my first post... That sounds like a baaaaaad idea.

Has anyone used MMO with Syntec or some other synthetic engine oil? Haven't been able to find anything conclusive online about this.