It would be close, based on the claims of the manufacturers. The plenum with the OEM TB is worth about 5 rhwp and probably about the same for the pulleys. Plenum is a heck of alot easier to install though, and doesn't require an air wrench (pulley swap does). So there's my 2 cents - plenum! Check www.modulardepot.com - and see their plenum shootout, parts 1 and 2...good stuff!
CNL plenum for sure. noticed a way bigger difference with that then pullies, I installed a 75mm t/b too, but I still think the plenum would be a better.
Yeah but plenum is a 15 minute swap. And with a TB, I think the gains would be greater. The newer GTs' pulleys are optimized for power more than ever, and there are still some gains to be had - but not as much as on the ol' 5.0.