I've got the Steeda UD pulley on my '06 5 speed. No issues.

Naw the GT never had the problem, the 4v required more oil and the oil pump barley had enough as is so the UD pullies increased the potential problem on the 4v. something along those lines but im no expert.

I have UD's on my 3.9L..It runs much better and in conjunction with the other mods I've done..it's all part of the package..and 318 bhp NA!!