just a question about upgrading to aftermarket pulleys.. ive heard it lessens the engine life, is this true?

It can if they are not balanced and sealed just right. They can cause premature crank wear and oil leaks.

so u can prevent this by gettin them balanced and sealed correctly?

The seal will depend on the install and quality of the materials. UR is a good company with good products. I think you will be fine here.

The balance is mostly in the build quality also. You can have your engine rebalanced with it on there but from what I know it's a pain and not worth it for the gains from those pulleys.

Not certain about the VQ engine but on the VG engine, they are not causing any issues. I have a UR set on my 300zx Twin Turbo and no problems whatsoever. However, many people have reported problems with Ebay pulleys.

Yes, there have been some problems with the other brands. I have not heard anything about the UR ones.

I would check around on my350z to see if anyone has had any issues on there.

thanks for the info.. i will make sure its balance and sealed right, also to balance the ur pulley the right way is this by using a special tool or just simply installed properly by an experiance tech? has anyone installed these ur pulley set and felt noticeable horsepower or had problems?

I have had the UR pulley on my Maxima VQ engine for over 35k miles. No issues. Just make sure your installer knows what he is doing.

Ref power. What I have noticed most is that there is no drag on the engine when the A/C comes on. So I guess you get something back by using the lighter pulley.