Hello,
So i have a 2005 LQ4, LS1 intake, Small delphi (truck) fuel injectors- using adapters, 98 vette filter/regulator, 3 wire MAF, all stock internals, long tube headers dumping into single 3" flowmaster cat. Im using a 2000 silverado base tune that i tuned for the 3 wire MAF and non-vacuum referenced fuel pressure regulator. I got the MAF table from a 2000 LS1 tune, and the IFR table from a 2005 Tahoe. Anyways, the car runs great with no issues... I went to get an emmissions test last year and got the guy to test it without catalytic converters. It passed the high RPM test fine =, but the idle was too dirty. I had 600ppm HC with a max of 200. So this year, i got the flow master cat and bolted on there thinking that would fix my problem. this time the HC was 880 with the cat on. So the test was much worse with a cat vs without... hmmmm My long term fuel trims are -1.56 on both banks and short term is plus or minus 5. So my question is, did i screw up on the tune somewhere or is there something else i am missing? I currently am running ethanol free premium gas, do you think i should dump E85 in and retry? Do i need to change the tune and injectors to do so? I think i can get some Flex fuel injectors cheap... Any help would be much appreciated. The guy who tested it said he thought that the cat isn't broke in yet- i literally unboxed it bolted it on and drove to the test station...