Hello,
I don't know how 'classic' this car is, but I have a 91 Oldsmobile Cutlass Supreme, with a 3.1L engine. The car has run great for a long time...but recently it has had a sudden problem. The car has hardly any power, and it sounds like it's missfiring a lot or something, very strange. A friend said the EGR might be clogged...or the cat...I'm hoping it's something simple like this.

Any ideas? Are these symptons common with these cars? It has around 175k miles on it.

Thanks for the help!