I have the HKS intercoolers and 555's w/dual pop and I would not dare go past 1.3 bars, even w/race fuel...20lbs is TOO MUCH. I have raced them either from the roll or from the stop. From the roll is no problem..from the stop you have to get at least a half descent lauch so you can get them and pass them 3/4 gear. I am not saying I lay the smack on them, but I am saying I beat them fair and square :-)