I recently replaced the CAT on my 90, 240 DL sedan, B 230F non turbo. The new CAT OD is smaller than whatever was on it before. The prior CAT was so bad it was rattling and got plugged up and then shut the car down one day. It started back up though.

However, since I replaced the old CAT the car does not seem to run much better with the new one. Does CAT OD effect performance? Not that I expected a rocket, but I did expect to see some performance increase. Btw, there are two holes in the exhaust system, one at the under axle pipe, and one about 10" in form the tailpipe end. That wouldn't effect performance would it? Thank you. Bruce

er well yes perf would be down if the ID is smaller and it doesn't flow as well......but a little bird tells me that you have some other problem(s) that indeed may be responsible for the poor running and the dead cat.

The cars response feels like a back pressure problem (Sluggish uphill). Could a lazy O2 sensor (7.90 volts max) cause sluggishness? Or how likely is that a piece of the CAT broke off and now has the front or rear muffler partially clogged?

Bruce