Ok fuel trims should be no more than 10% when you add short term and long term together. Under a heavy load they will jump a bit, but not usuallylong term. Long term trims will tell you that it is trending lean, or at least the computer thinks so. Dark plugs, fuel saturated, computer thinks its lean, and cant rev very high. Really there are 3 things that really come to mind. Low fuel pressure, restricted exhaust, or jumped timing. I vacuum guage would tell a lot here. Lack of exhaust flowing past the O2 sensor will cause these kind of issues. The timing is retarding because the PCM is detecting a lean condition and trying to pull timing to avoid detonation. Need to find the root cause of the lean condition, or precived leab condition. Vacuum guage and a scan tool i can walk you through getting the problem pinpointed.
