the original cat was empty of any material. it spewed itself into the old exhaust system. i replaced the cat back pieces a few months ago and ran it just fine. i am putting on a new cat tomorrow and was curious if i will notice any differences. the current system would set off car alarms. the gas mileage is a little off but there are few things that still needed to be checked.

benjamin
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1989 740 GL

It will be warmer under your car, and the cat provides about the same amount of muffling as a noisy Flowmaster. I'd be interested if you could do a fuel economy comparison.... I have seen some good improvement on removing an older cat, but a new one shouldn't hurt much.