ok most likely going to get the LT's but i am seriously interested in the spydershaft and udp's. should be about the same price since if i do the shaft and udp's i will install them myself.

 

Depends on what your priorities are. I love my LT's, off road h-pipe, muffs,my CAI/Tune, and my 1-piece driveshaft. All made a difference in performance that personally,I felt in seat of pants performance. And I'm at that point where it will take a major investment to get more out of this little 4.6. It runs great, has >300rwhp I would assume now that everything is tuned right (haven't re-dyno'd but I need to).

If you just want more speed and don't care about daily driving experience, go ahead and spray w/nitrous. No cheaper bang for buck performance mod available bar none.

If your plans include FI later, I would suggest you work on exhaust. That was my plan. LT's, hi-flow or no cats and axle back system. It will sound great, give you ~15 rwhp and you're working toward your final goal of maximum hp with FI. I would work on exhaust and cai/tune first, then driveshaft which is a great mod. Then think about spray or FI.

I never thought about underdrive pulleys since they would have to come off if I installed a s/c. I was torn on getting a CAI since that will also have to be probably tossed when going to FI/SC.