I have a 400W amp and a kenwood db+ sub and I am interested in getting a underdrive pully and I wanted to know if there would be any adverse affects on my car.

 

i doubt the udp will affect anything with your system

i have two precision power amps and every thing is fine

 

I was worried about the same thing before I got mine. I have a 400W Kenwood pushing one 10" sub. Everything works great. The one thing you MIGHT notice is your headlights will dim if you are in gear without moving, and your AC on. The only way I could tell my headlights were dimming was if I park my car right up to a wall to see the reflection of my lights. But, I think my headlights dimmed before I got my UDP installed.

I can't tell a difference in Power Steering or Air Conditioning, either. But, I can tell a difference in low end torque and throttle response.