Here is 2nd round of testing.
Tests spread across 2 days but weather the same for both days at about 50 degrees.
Two tests with X-pipe done today to then compare the tests of yesterday which was one run with gutted CATs and one run with X-pipe.
Keep in mind the vette has 3.73 rearend gear with 335/30/18 tires with limited traction but all testcases are equal with that issue.

Also when values go negative that is due to wheel spin and standing start and having to make 4 manual trannie shifts.

Same road used in all tests.

Again X means with X-Pipe and C is when gutted CATs were used.

Clearly correct placement of X pipe ( using 3 inch to collector but then 2 1/2 inch pipe to exhaust pipes) as you see the first 7 seconds from dead launch X pipe is winner as to HP, Tq, and MPH

For this test we retuned the PCM for a perfect fuel trims around zero and WOT AFR at 12.8:1.
Also changed radiator fans coming on at 200 degrees to 185 deg

With the tune horsepower increased from 475 to 513 flywheel.