Mine did that once. My cat was clogged from some debri I did not get out when I gutted the pre-cats. Luckily I could get it out by cutting the cat off and clearing the pipe then re-attaching the cat. I found it though by disconnecting the exhaust at the down pipes and the exhaust manifold and rev'ing the engine and it actually went to redline. Before even in nuetral it would not rev past 3500RPM. This clogged when I was on a highway and the engine could not go past 2500RPM and hold speed. This sucked big time.


Edit: Also you do not have to take the bolts all the way out, there are only 4, you just need to loosen them enough to make the exhaust leak. Lose but not all the way out. Enough so you can seperate the exhaust to relieve pressure. Then if you can rev and run right you have found your problem. Do you use fuel injector cleaner ever? The cat's get clogged normally with that kind of mileage and a piece of carbon or pieces could have blasted out of the cylinders over time and caused it. If it is that. With those miles though I am betting on Cat.

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~Jamie
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2003 Pewter C230K SC C1, C4, C5, C7, heated seats, CD Changer, and 6 Speed. ContiExtremes on the C7's.

1986 190E 2.3 Black, Auto, Mods to come soon.....