Oh I agree with you there, the problem is that any given up grade will respond differently in almost every gun. There will be a general trend for sure (TBB will increase FPS for example) but direct comparisons are hard. For example - I needed to get my FPS down below 340 to use a gun at the Malls. M100 should be right but even an M90 pushes a couple of my guns over because I've also improved my airseal (nozzle, cylinder head, piston o-ring etc). In addition to that a combination of upgrades will change how a gun responds depending on how that particular combination works with the other component parts - the TBB you choose for an M16 won't respond the same as the same ID TBB on my M4 for example (as it has a 280mm long barrel).
Maybe think about what you find a problem with your specific gun and ask if anyone has an idea to improve that aspect.
And don't be offended if the answer is either "move closer" or "learn to shoot better"