It's a multiplex profi speed digi servo, which I wouldn't recommend for the steering anymore. I now run a KO Propo 2174 in there.
Essential upgrades are:
Front and rear chassis braces.
Front brake disk (or the quad conversion).
High torque metal geared steering servo (Hi-tec 645 minimum but still that aint that good).
Fuel guard (to keep the disks clean).
Ball link brake linkage set.
Hexheads screw set. (not really essential but mot than recommended)
Recommended Hop-ups:
CNC Knuckles.
One peice pipe.
8 port race/pro engine.
Starter box.
White/blue/purple springs.
Stronger Brake/throttle servo.
New style CNC shock towers (Stock on the Pro UK).
New style Gearboxes.
Tips to make thing last longer:
Boil your wing, front and rear bumper for about 15 minutes to soften the plastic and help prevent it cracking if you tumble. (That goes for any buggy).
On the steering posts there is a spring and Nut. Wind this nut right down to the chassis to releive tension on the servo saver allowing it to slip earlier and not kill your servos so readily.
Strip down the entire buggy and rebuild it before you run it for the first time.
Finally do not rush the break in of the engine. Follow the instructions given in the manual and it will last at least 10 gallons. Also If the temps do get to high stop the engine immediately and always return the piston to BDC upon shutting it down.
Then after you've Hopped it all up you'll be close to this...
