OK...........so I've been having some problems with my OS 91FX and I'm going to change out the needle valve assy but now I'm also wondering if I should use a lower nitro content. I've been using 15% nitro and 18% lubricant and I'm considering going to 10% nitro. I've heard that the larger engines just don't need the higher nitro. Only thing is most of my engines are OS46FX's so I don't know how they'd run on the lower nitro. Where I live it's at about 3500' elevation so I took the advice of the locals and started using 15%. Where I lived before I used nothing but 10%.

Opinions?

thanks,
Andy