2003 CCSB 4x4 Chevy 1500HD LQ4 and 4L80E with Speed Engineering 1 3/4 LT headers, full Speed Engineering 3" true dual exhaust with X-pipe, E-Fans, K&N CAI, and some tuning done by me. All was well until I installed the headers and exhaust. It was immediately lean which was to be expected after the headers and exhaust install; however, the problem is now it is sometimes very rich at startup; even if it not a cold start and at normal operating temperature. IT will idle rough and show a reading of .67 -.81 on the wideband set for Lambda. After a short drive the idle returns to .95 - 1.05 with no rough idle. I believe the wideband is reading correctly because it smells very rich when it has the rough idle and smells normal when the gauge displays close to lambda. I am also aware it should be a bit rich at cold startup which is not the case when restarting at normal operating temp. Am I missing anything in the tune for idle that would cause this. This was not an issue until after the headers and exhaust. Also the issue is not always present, but instead is hit and miss. Any help is appreciated so thanks in advance.
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