i just bought under drive pulleys for my 05 150, and i was told that the alternator wont charge right after i install it, and that it may even burn up may alternator. also can you see a difference in power.. i already have aem air intake, airraid throttle body spacer, grenatelli diablo predator programmer, grenatelli mafia, and magnaflow exhaust..

 

I have had pulleys on my truck for over 10K with no issuse I even have a 1000W system in my truck, they also give you better power off the line.

 

I had them for about 5000 miles took them off to install a Roush super charger they are not compatible. because the bottom pulley wont fit on the after market under drive pulley. but in your case the under drive pulleys are a pain in the a$$ to install you have to grind a big chunk of metal off the front of the engine to in stall the water pump pulley . if you can swing it go for the Efans and forget the under drive pulleys

 

I installed the underdrive pulleys when I installed the Troyer Dual 16" Electric Fan kit and no problems to report.

In fact, I believe my seat of the pnts dyno makes me think I get to use more of the hrsepwer my little engine makes.