im far from being an expert on this car, but dont cen do a "track kit" with smaller pulleys, and/or pinions and spurs and belts? im sure i read somewhere that they do something like that. might be worth a search... just a thought mate.

other than that, what pinions are u running? u could try some smaller ones, just be careful with the gear mesh and all that... unfortunately i think the 42t green gear is the largest spur that cen make for the alloy hubbed gears that i believe the ct4 car uses. so ur left with spurs, belts and pulleys to try to get the acceleration ur after.

sorry i cant be of any more help - good luck

oh hang on - just had another thought (2 in a day - jesus...) erm, seeing as the alloy hubbed gears fit the funfactor, then wont the larger, red, plastic spurs from the 2 speed mt fit on the ct4? i dont see why not, so long as there is a cutout in the chassis so they can fit in there. if they will fit then for about a fiver or so u should be sorted. i was thinking of the 47t and 43/44t spurs, depending on ur pinions and mesh etc.

hope that bit is a bit more helpful...