PontiMANIac

Under acceleration at 1/4 or 1/2 open throttle, the engine in my 2000 WS-6 seems to lag as soon as it hits 2500 rpm and continues to feel like I'm pulling a bus unless I mash the pedal. I have an m6 tranny and it doesn't seem to matter what gear I'm in although when driving it sanely I'm usually in 2nd or 3rd at the time it happens. I almost feels like the engine is retarding or the engine breaking caused from compression is causing a problem. (Again under WOT there is not problem) Does anyone else have this happen? The engine has 59k miles on it and runs excellent so I don't know if this is normal or not but I don't remember noticing this issue when I bought the car 2 years ago.
The only mods are an SLP lid, Borla cat back, TB bypass, Diablo Predator tune. (Engine lag is noticible with stock tune or performance tune).
Please advise if you have any ideas.

Flow Wizard

Have you checked your plugs to make sure your running under all 8cyl?