I can't help you with your question really, but can say that removing the cat altogether does free up the exhaust a lot. I installed a Kennedy 3 1/2" exhaust system and left the cat out. That combination (along with ceramic crosover pipe) made a big difference in seat of the pants acceleration. My state does not even do a visual inspection on diesels emissions. I know CT does require emissions tests on diesels, but do they visually verify that t he cat is there?
1995 Chev K2500 6.5L TD X-cab, LB. Kennedy FSD,Cooling Mods,exhaust. 118,000 miles<br />2003 K1500 LT Suburban, gas. Gave up on Duramax suburban. Not happy about it.