I'm considering purchasing a RMR exhaust and maybe a downpipe and i'm keeping my stock air box for now. Will i notice any improvements without a re-tune. I spoke to a fellow owner at the HKS event in SoCal and he said he lost power when he added a HKS exhaust and intake with a re-tune.

thanks

 

dats wierd .. cause i have a custom exhaust, stock air box, BOV N a fuel pump.. runnin 21p... i did feel a great difference .. plus its not flashed yet.. so i dunno....