does anybody know the reason why my truck does this?

[Finnster]

I would recheck your alignment in back and front. This is for an emaxx right? I noticed w/ my Revo that since you have tie rods in both F and R, I had the F just a little misaligned to the L and the R a little misaligned to the Right, it would pull to different directions depending on the power/weight to what wheels. I'd use the trim to center it one way, and it would sometimes be straight... but then at other times it would pull.

it wasn't until I finally put it on a setup board and got it right did it ever track reliably for me. Eyeball method was never quite good enough for me.