I noticed that my Rpms havent been up to were they used to b after I installed some 5 Gsk 2 weeks ago and didnt think much about it so I changed a few things and nothing is really helping . The shop that put them in said I may need to put the 4ks back in I was like huh? he said hes been talking to others and that I might b better off with the 4k untill I have more pump work done and what not , so I started doing some searching on here and noticed the same thing others have tried and they have lost RPMS so is this a hit or miss thing ?