What do people think about the underdrive pulley and is it worth the cost or if replacing this isn't a good way to go what else should I spend my money on, I have 4.10 gears and a lsd getting installed Tuesday, I have diablosport pred. tuner, CAI, and exhaust system, what would be another good upgrade for a reasonable cost.

 

I heard you can get between 2-5 hp. Seems like a bit of expense for so little added hp.
Then again, every little bit helps.

 

You have an 05 so your driveshaft doesn't have lock-rings/snap-rings on the universal joints. I also had a vibration at 72-73 mph that just wouldn't go away. An aluminum driveshaft cured the problem and is much safer then stock. Stock shaft is 30 lbs. and aluminum is 17.5 lbs. Car just felt like it has more pep. No added HP but like gears lets you use your horsepower to better advantage. I think Shaftmasters gets about $450.00 now. Let him know your a member and he ships free. The 4.10s & T-Lok will make a VERY BIG difference too!