[KingLT1]

RPM just did a experiment with a NA Corvette. Fran did 3 pulls back to back. One @ 12.8 afr, 11.5 afr, and 13.5 afr. Guess what, they were all within 5whp of each other on a 400-430whp car. The AFR isn't costing you power but the timing is. The LT1 knock sensor sensitivity is way too sensitive because GM set the engines up with the ability to run on 87. So that combined with high compression is why they pull timing very easy. You need to find a competent tuner that knows how to tune these DI engines correctly.