I installed a flowmaster muffler a while back which made the exhaust sound way better. Since then, it's (quite suddenly) got really quiet and muffled-sounding (as if it's clogged up with something) -also occasionally it smells a bit eggy and does tend to stall a bit more offten since this has happened.

Could this be the cat/convertor? (it's never been changed in the 5 years I've owned the car) -I was thinking of going for a universal one (if it's that) -does it involve chopping around the piping? -any other major disadvantages from stock?

Many thanks
Andrew

 

It is my understanding that if you smell the "eggy" smell, the cat is starting to go.

I know that when I changed mine out, my emission numbers went down and my performance went up.

Now, the one I got was a OEM replacement from Autozone for like $65 but it was a lot less restrictive than the stock one that was still on my 'Bird. There are some real good performance ones as well. As a test, remove the cat with a straight pipe and see what happens. But IMO, if you see an improvement, get a new cat as soon as you can. If you do not see an improvement, you may have other areas that need attention.

Your results may vary.

 

Sounds like your cat is gone.

If cat is good, the pipe(s) after the cat should be hotter than the pipe before the cat.

If cat is bad, the pipe after the cat will be cooler than the pipe before the cat.

 

But the eggy smell is also normal for a new cat, so you can't necessarily go by that.

Also, just because the cat hasn't been changed in at least 5 years doesn't mean anything either. The cat should last forever, theoretically--but we know they don't.

But it's the stalling issue that's the thing to take seriously. That could definitely be the cat. But you also said it "tends to stall a bit more often," like it's always had some stalling problems. Your engine should never stall. You might have another problem besides or in addition to your cat.

But if you replace it, be sure you know what you're shopping for. You have an '87 TPI, right? So your cat's inlet and outlet are each 3". An auto parts store selling a universal cat is likely to sell you one with 2 1/4" or 2 1/2" inlets or outlets.