Let's see the 3rd! The way this post flows I figured this was your last one. That auto really sucks up the power, doesn't it? I don't suppose you dyno'd it stock? I have an 04 C5Z myself.
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Most with longtubes make 375-385. I also have a 3" catless x-pipe, a ram air intake, air bridge, coupler, leaned out PE a little, and 20# less clutch than stock. I figure I ought to be on the high end of that. I have a mid sized cam for it, I want to see what it dynos after that. Hoping for 420 or better, but we all know the numbers tend to fall short of what we want. If I had to guess, your exhaust took on a more shrill note with the goodies?