ok so here is my next question. is there any difference in having gutted cats verses cutting the cats and welding in straight pipe. im talking performance wise. which way would be better.

 

The straight pipes would be better, as there would be less turbulence and better exhaust velocity where the exhaust enters the cat converter chamber. On a mildly modified engine, you may not feel the difference, but straight pipes would be the best way...if your state emissions laws allow it.

 

Cats are federal emisions, its illegal in all 50 states to gut them. Just some states dont check, or like FL they have no sort of safety inspections at all. There is some POS vehicles on the road there, I hit one who had no tail no tail lights and cut right infront of me. It went as my fault, which is BS. With just gutting the cats and leaving the shell there your less likely to get caught. If they peek under and see them there on a new vehicle most wond even try the sniffer test.

 

i have a stock 1999 5.3L. i cut the cats off and cut the top of them open to gut them. i then took and welded a straight piece of pipe inside of them just to keep appearances up. delaware does check to see if they are on there. i bought a set of O2 sensor simulators from casper electronics that plug into the plugs on the O2 sensors behind the cats and send a false signal to the computer. seems to work pretty well, ive had it done for 4 years now and ive never had my service engine light come on. couldnt be more satisfied.

 

with hptuners you can turn them off and then the ecu will set it as they are good. so they can plug up a scan tool and it shows o2's set.