I put a smarty on my truck and i run it on sw4 just fuel. Cause i have a comp that i run sometimes. Most of the time i run just the smarty but when i kick my truck out of overdrive i can hear like a knock of some kind to it. Can cut the comp on 1x3 and it all but goes away. I don't think it did it before the smarty if so i couldn't hear it because i had a open filter on it. Now i have my stock box back on because K/N sucks:w: What could it be?? Was thinking timing knock but i don't know how that would be because i'm not using timing settings. It sounds bad and has me wanting to take to smarty off.:thud: Thanks for any help!