One advantage we LS owners have is that we've had a couple more years to tweak our 3.9s than the TBirds. The 3.9L engines run low on air, since the airbox is designed to keep the intake roar quiet instead of supplying the necessary engine air. You can combat this a couple of ways but they require some surgery to the airbox, which you may not want to do. Couple the changes with the Magnaflow cat-back system when it comes out and you will see about a 10-15 hp and torque gain at the rear wheels.
The most radical approach is to cut off the entire bottom of the airbox, except for the side that is closest to the engine. Adding a flexible air hose from the front grille to the area right behind the
headlight will bring cooler air into the area. This gives you the most air into the engine possible, keeping the stock airbox. I'd recommend a
K&N filter as well. You can feel the engine breathing a lot freer from 2,500 rpm on up. Plus as an added benefit you get a great "power roar" from the intake system, similar to the old four-barrel moan.
The other way is to just cut some 2 inch holes into the front of the airbox bottom. Route a hose from the grille area but do not hook the hose into the airbox, otherwise you risk water ingestion which will hydrolock your engine quicker than you can say "Oh ****".
If anyone wants more details or pictures you can email me at brian.gowing@llsoc.com
