hi  only thing i did do was remove the stock muffler  baffle15 % omega fuel-13,200-13,400   RPM'S on the ground -11/5  APC - might add -    a great sounding engine-    a lot to love- -one of the best engines for the dollars-just took a long break in time to hold a good idle and top endbut worth the time- (4-tanks of fuel  )-no need for expensive 50 size engines with this engine- from s/t around   do all you can to keep the muffler in place-only down side of this engine  i can seeis muffler design-that applies to all s/t enginesblue loctight all bolts