What would you reccomend me upgrading on my Nitro Rush?

So far Ive got a racing clutch, Fiberglass brake disk, graphite upperdeck, graphite shock towers, and Pro-line Dirt hawg tires.

I'm possibly thinking about getting a new Engine but now sure what kind yet. Also what kind of tuned pipe would you reccomend?

I'm not very impressed with the steering on the Rush either. What can I do about that? I was reading up about getting new servos can anyone explain a little.

Any recommendations would be thankful. Also post links to parts if you can.

Nick