The first thing you should do is get the kart scaled and see how your weight distribution is. If you find your heavy in the rear then consider getting a front porch extension for your kart. That will alow you to move the seat further forward and shift weight forward. Then basic chassis adjustments and possibly diffrent tires or combinations of diffrent tires front/rear might be usefull. Weight is a big big deal and it’s hard to compete when other karts are much lighter so all you can do is try to use the aditional weight where you can.