Good evening,

I'm running a OS 91 fx with the macs 1062 pipe and a KM header.. Prop APC 15x10 prop at 8900 rpm or the 14x10 at 10,000rpm with 25 % cool power and the OS F plug, fuel tank is on the Cg and no pump or header tank just pipe pressure.. This moves the 8 pound pattern plane very nice.. great vertical... Your pipe lenght should be about 21 inches to the first baffel.. Some times you may have to add a head shim or two like .007 works good....My engine is all stock !!!