How many RPMs can you typically add to an engine after modding it? I was browsing some of the modifiers websites and came across a new one who make some "amazing claims". Here is the one that caught my eye: "Expect 15,000 rpms over a stock one and 50% more torque". This is just one of them but they are all in the same line. Is this even possible? How could one make such claims with so many mechanical variables? Even a dyno is just a "guideline/estimation" and not an exact method. I'm not trying to bash anybody, just trying to get a better understanding and see if these claims are possible to achieve. Please discuss.