I meant good tyres, good suspension, good brakes, make sure all bushes etc on the car are in good nick.
Really $4k can go far, or not really anywhere. In terms of performace I would have spent $1k max on the engine, and got the most out of it. Just doing the right mods getting good gear, and paying the right price for it. But then suspension, brakes, gearbox, everything else is up to scratch.
Just my oppinion anyway. Even split it up a bit.