I have a 99 half ton Chevy pickup. Not Silverado. I had a cat delete exhaust put on and I only get about 8 MPG.
Asked by s_houghton1987 Apr 11, 2017 at 09:32 PM about the 1999 Chevrolet C/K 1500 LS Extended Cab 4WD
Question type: Maintenance & Repair
3 Answers
HUMMMM.BELIEVE IT OR NOT YOU NEED BACK PRESSURE EVEN RACE CARS ARE USING THEM NOW...OK..YOU DID NOT SAY WHAT SIZE PIPES WERE STOCK..WHAT SIZE DID YOU PUT BACK INTO IT??/ 1 OR 2 CATS/MUFFLERS..THE NEW BRAND NAME OF THE MUFFLERS...IMPORTANT ALSO MOVING ON DID/HAS THE AIR INTAKE BEEN UPGRADED TO MATCH THE SUSPOSED EXTRA EXHAUST FLOW???? AN EXHAUST CROSS OVER??1 OR 2 TAIL PIPES/EXTENSIONS????
Has nothing to do with backpressure.......you removed the O2 sensors didn't you?
s_houghton1987 answered 7 years ago
upstream O2 sensors remain downstream were tuned out in the computer