Novarossi 21BF is by far the best bang for the buck in the nitro engine department! I have a good 3-4 gallons on mine in the MBX5 and it runs great. Its never flamed on me and gets good run time. I use a 9886 with short off-road header. The motor was crazy tight for the first two gallons. Then it will loosen up and scream up top so don't get discouraged if it feels sluggish on top. It just needs a lot of time to breakin.
Tonys Screws LLC
High Grade Alloy Steel Screws, Screw Kits and Mugen Parts