RE: best way to tune a monster truck?..
Break in per the manual like they said. I happen to know the 24.7 motor in the Mammoth comes with good directions for break in. Follow them to a T... No sense in deviation. If I am not mistaken, the 24.7 calls for short blips on the throttle in 2-3 minute increments with 5 minutes in between increments, while leaning a little each time, until there are 30 minutes or so on the motor (10 cycles). When you are dialed in, don't over lean it. Get yourself a temp gun if you can.
Works like a charm. My 24.7 ran AWESOME!
Key points to remember-
1. (broken record) Follow Directions
2. You will lean the motor by turning the needles IN (clockwise); You will richen the motor by turning the needles out (counter clockwise).
3. Keep some spare glow plugs - McCoy MC-59 or OS A-3 or OS A-8's. I fouled 2 glow plugs while breaking in my 24.7. No biggie there. I NEVER had luck with the McCoy MC-9 after break in, even though XTM recommends them. An OS A-8 worked AWESOME for me.
4. Use a fuel with a higher oil content (20% nitro with ~18% oil content) Traxxas Top Fuel is AWESOME for breaking it in.
5. The 24.7 AFTER break in likes lower oil content fuels (20% nitro with ~12-13% oil) like Trinity Monster HP. I didn't have much luck with Top Fuel after break in with the 24.7. I noticed a large difference when I went to the Trinity. Some information on XTM's forum site supports this.
Good luck!