Let's start with belt. LOL
This is how my belt is tensioned, 2 different cars.
JRX-S Type R This one runs somewhat tight belt since there are no tensioners.
E4RS/FS sumthing This one runs loose belt but there are tensioners that prevent skipping unless i brake 100% or accel with crazy torque.
Next you check ur diffs if they are slipping. How i do it with my cars is Hold the main belt and 1 tire Down, then try to rotate the opposite tire, it should not rotate. I think thats how you test it. Now ont force it to rotate LOL
Other variables are gearing it down smaller piniong this will give you punch less top speed.
Or Gearing it up for top speed but motor will take longer to get there.
Then you have ESC timing you can advanced the timing to motor start cooking it. =D
Check if you transmitter has throttle control/Punch control of some sort turn it off.
So it doesnt delay the punch.