[Aussie Mike]

The better examples of these tuners that don't know **** seem to be able to take an internally stock unopened LS1 and with the addition of a good set of headers, a cold air intake and careful tuning and push it down the 1/4 mile in 11 seconds. They aren't doing it with 1 5/8 headers though. The dyno curves I've seen for these motors show an overall increase in power right through the range. It might seem like there is a loss of low end but that's only because they gain so much in the mid range and top end.

Perhaps you should talk to some other tuners than the ones you are using at the moment. After looking at Bretts car I noticed it had a 3" neck on the air filter stepping up to 4" for the MAF and throttle body (Something to do with fluid dynamics?). I also couldn't find the IAT sensor anywhere and this is crucial for optimizing ignition timing.

I have heard that one of these tuners that doesn't know a pinch of **** has just re tuned it and it's making significantly more power than it was when it rolled out of your shop.

Cheers