I have a F115 TJRA Jet that I used to run at 5800-6000 RPM, now I only can get 5100-5200 RPM at WOT. The motor sounds great,starts great, idles great and no missing or sputtering, just low RPM. I have put in new plugs, changed remote fuel filter, cleaned onboard filter and had injectors cleaned. Compression test cylinders 1-3 165 lbs and #4 170 lbs. I'm at a loss as what to try next???