its all about car setup. the trick is to get the handling balanced. What tyres are you using. Tyres are the major part of the setup and if the tyre selection is wrong your car wont fast. Ask what other people are using. Or try a whole different bunch of inserts, each run try a different set of inserts. Glue the outside of the tyre and partially glue the inside of the tyre so you can peel back the rubber and change the insert. Just be careful that you dont tear the belting.