What shoes are you using in your buggy? I have a Kyosho MP777WC, had a MP9, sold it, just didn't race it enough, and better resale value, running a RB WS7III, with 2the carbon shoes, and 1that aluminum, with 1.0 springs, works well, very controllable, and predictable, with using 1.1 springs, the engine has to spool up before the clutch engages, creating a bit of lag, I don't care for that myself, when the K10 your using has that lag, or bog, that could be the problem with springs, or even the pipe combo your using, I think your engine is to lean on bottom, an fat. on top, those engine do tune a little differently, mine was kind of a headache till you get about a gallon of fuel thru it. Your temps are good, maybe even a little low, I have used RB engines for over 10 yrs. For the most part, they seem to run the best around 240-260 range, using 30% Nitro content. Try 1 hour out on bottom, 1 hour in on top, your idle gap may need to close up, you want about 7mm. Give it a try, see how the change is, bring your temps up also, at least to 220-235.