This gas or electric???? If gas, pick up some 10 %nitro based fuel. It should speed it up. If electric, I belive some one sells more juice for battery packs. You can allways change the engine and buy a more expensive one but thats $$$.
take out the original motor and batts....replace with a mabuchi or graupner speed 300 and some blind brickpack 6 cells 1000mah ni mh batts....Or even better buy a HPI micro rs4. i got mine onn speed 300 and i can reach speeds of 30mph and its a 1/18 car. if your car is larger then 1/18...put in a orion 540 motor but i am sure you will have to replace all the electronics so tis not worth it. Ask jevries...this guy never runs outa ideas.
You wanna turn this car into a lowrider? otherwise the same story "of search for a RC only forum" applies here too.
I'm sorry I don't wanna make the rules on here but matters of making your RC car more speedy doesn't belong on here...if this handles about a "turn into a lowrider car" I say okay let's talk buisness..otherwise try to find an RC orientated forum or website.