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The rear suspension is also done by PSM. PSM parts include all of the rear suspension links, the crossmember bushings and the knuckles. We really like the PSM parts and Matt has had a lot to do with the development of the PSM parts that you can buy right off the shelf.
Since the S14 has pretty decent rear geometry compared to the S13, the team has not relocated any of the suspension pick up points on the crossmember. The upper links have been relocated on the PSM knuckle to keep the camber curve, anti squat and roll centers in check. The PSM knuckle is designed with a true 25mm drop so your ride height can be kept low while still maintaining generous bump travel. The PSM knuckle also has built in provisions for dual Wilwood calipers.
Getting the roll center right is a big secret toward making an S chassis stable in drifting. Too low of a roll center makes the car twitchy when running a grippy setup. The PSM knuckle does a really good job of getting the roll center right even at low ride heights.
One of the coolest things about the PSM suspension is the Limit Break adjustable toe steer toe link. You can adjust the rear suspension to toe in, toe out or be neutral under roll. This is a great help in dialing in how your car behaves under drift and how much throttle the car will take under drift without over rotating. Matt's car is adjusted to the neutral position here. 
The rear shocks are PSM 3-way adjustable coil overs with independent adjustment for high and low speed compression and rebound damping. If you were worried about the springs being plated and hydrogen embrittlement causing them to fatigue quickly or crack, fear not, that is actually powdercoating.
The rear spring rate is 7kg which is stiffer than what most S chassis guys run in the rear. Matt has given a lot of R&D time to perfect the valving and the spring rates of the PBM suspension and it shows, his car is fast and can pull off some amazing stuff.
A Speedway Engineering IRS quick change differential is used. Most of the top pro cars currently use quick change diffs. Fredric Aasbo and Ryan Tuerck are two of the exceptions. The idea of the quick change is to find the gear ratio which fits the engine's powerband and requires the least amount of shifts during a run. Typically its 1-4th at the start with one downshift through the course for V8 powered cars. The Speedway unit uses a solidly locked spool instead of a limited slip differential. The pro field is split on this as many of the top teams are going back to limited slips after almost exclusively running spools for the last few years.
Matt's unique pedal to the metal driving style dictates an unusual gearing strategy. Matt gears a lot higher than most of the other pros and runs a lot of wheel speed, typically twice the actual speed of the car Leaving the pedal to the floor, he uses angle and wheel speed to slow the car, kind of like vectored thrust on a boat or fighter plane! The extreme wheel speed also makes for quite a smoke and noise show.
A Progress 3 way adjustable 24mm rear swaybar is used. You can't see it but a custom exhaust is run on the the car made of 3″ Vibrant 304 stainless steel tubing from the header collectors merging into a oval 5″ Vibrant 304 stainless tube under the car. There are no mufflers at all, just an open exhaust. 
