Even if you do swap TB's, even GT's make very little gains from bigger TB's NA. Unless the 3.7 has a poorly sized TB, a GT won't net you any gains worth the cost of a tune. CAI either. For a V6, I'd recommend HF cats or O/R pipe, gears (4.10's) and a tune. The tune is going to free up all the power, the parts are minimal gains. Gears won't free up power, but the seat of the pants feel and ET will improve. Personally, I'd forget all that and just go straight to a conservative turbo kit. DIY or off the shelf kit, something small and snappy. Still keep the efficiency of the V6, have V8-like power on tap.