The biggest gain in power fr me came from the change in gears; after that, I would say the e-fan was the biggest change. THEN the TB and spacer; mine are actually a 4.0L TB bored out to 62mm with a 62mm spacer. Talk to BountyHunter, he sells them... And I DO recommend the mod, as (especially in the mid throttle) you will feel a much crisper throttle response. So long as you do not expect HUGE improvements from any one mod, I think you will be happy (my Jeep has man mods, and all together do make quite a bit of difference; and on top of that, I got a new, more aggressive MOPAR cm going in soon)