this is a good point often missed from 4dv8- stuffed cats are a real problem in older high mileage tanks. i had a severe slowness problem particularly when i warmed up my old sl6 dodge. tried many things. it even defeated a master mechanic of my acquaintenance. uncle moe said to thoroughly check engine breathing particularly the exhaust. noticed hot exhaust pressure out the tailpipe on my hand(gloved) did not change much from idle to fast idle. disconnected the flange where the exhaust pipe connects to the cat and ran it around the block. the old power was back. didnt do it too long as prowling coppers would have been tipped off by the noise.some rookie working for his quota would have hit me with a $500 public nuisance ticket. cleaned out the cats honeycombs which were full of carbon and clogs. problem solved and didnt cost me a thing. dont you like it when the poor guy wins? told my master mechanic and he said he never actually saw such a thing but had heard of it when cats first came out in 74 tech bulletins. regards oldduke