So I was all ready to go and order a MBRP exhaust and then realized that I already have a 3.5" exhaust and am not going to pull the cat off. Will a 4" system really gain me anything if I don't put on a new downpipe? Would a 4" cat-back be any less restrictive than just replacing the OEM muffler on my factory system?

And last but not least does anyone make a highflow cat for these trucks?

WAskier,


You will drop your EGT's, the turbo will be able to spool up quicker, and some folks report MPG increases too! The cat that comes on the LLY trucks is actually pretty OK as far as flow goes with cats. It's not like the old style that basically clogged up in 75,000 miles etc. You will get the lowest EGT's by removing the cat, but were talking apprx 25-50 degrees overall difference. We get customer reports all the time on the cat back system that it does exactly what they wanted, on the few that need extra EGT help we get them into the Cat test pipe and they are OK then.


Mark @ DPPI