When Polaris introduced the RZR XP 1000, it was obvious a four-seat version would follow. The question was would it be a year later, following the cycle that had been established by its 800cc and 900cc predecessors? But those waiting for a XP 1000 with room for four didn’t have to wait as long as they thought. Just a few months after we sampled the RZR  XP 1000, we found ourselves on the sand dunes of Glamis shredding the 2014 Polaris RZR XP 4 1000.In the simplest of terms the XP 4 1000 is a stretched four-seat XP1000. The same 999cc ProStar Twin that powers the XP 1000 is used in the XP 4, cranking out a claimed 107 horsepower. Dual Overhead Cams (DOHC) actuate four valves per cylinder to intake and expel fuel provided by the dual EFI throttle bodies. Between the two 1000 models there is no difference in the engine department, and that is a good thing as there is little doubt in our minds that this is the best performing side-by-side mill on the market.Putting power to the dirt is done via Polaris’ PVT drive system that uses continuously variable clutch sheaves and a belt to drive a transmission with two forward (high and low) gears and a reverse. The transmission also features parking and neutral selections from the center console mounted shift lever. The clutch has been tuned to respond to the additional 219 pounds of vehicle and two extra passengers.Seating for the rear passengers extends the body and wheelbase of the XP 4 1000 by 27 inches for an overall length of 146 inches, stretching 117 inches from tire to tire. That extra space gives enough room for full-sized adults while not having to resort to the stadium-style seating in most other four-passenger side-by-sides. Polaris explains the flat seating arrangement is important to keep the center of gravity lower for better handling in the corners. All four seats are heavily bolstered for a secure feel when the G’s increase and feature Dryseat technology to resist moisture from rain or cleaning. Standard three-point automotive seatbelts secure the occupants.In the suspension department, the front and rear shocks receive stiffer spring rates and revised damping rates. The rear Walker Evan’s Position Sensitive Needle Shocks also have a larger shaft diameter (7/8” vs 3/4”) and longer remote reservoirs to handle the extra load. The compression adjustment range is also wider for both ends allowing for fine-tuning of the ride depending on the number of butts in the seats.Glamis is one of the greatest places in the world to drive a UTV. The seeming endless dunes offer up a virtual rollercoaster ride with hill climbs, bowled corners and massive jumps. While the dunes are epic they do require copious amounts of power and suspension to navigate at speed, and according to the spec sheet the XP 4 1000 is well equipped for the challenge.Getting into the XP 4 is hassle-free thanks to very solid doors that open and shut with ease. Adjust the front seats forward or back to suit your preference, buckle up, turn the key and you are ready to go. The engine fires to life with a pleasant idle that is subdued enough to not annoy but still conveys that there is plenty of go hidden in the right pedal. Gear selection is smooth, and the gear indicator in the center-mounted digital and analog gauge is easy to read. Legroom for all four passengers is adequate.Stepping on the gas brings forth a surge of power that is snappy in both high and low gears. Speeds at the dunes are usually high so we spent most of our time in high gear. Polaris claims the XP4 1000 is the fastest accelerating four-seater on the market, and my seat-of-the-pants dyno agrees. Power comes on strong right off the bottom, tapers off a bit in the midrange and then pulls strong again approaching the top end. It’s crazy the speeds that the XP 1000 models can achieve without fuss. In the dunes we regularly saw the speedo creep above 70 mph. That should translate to somewhere above 75 on the dirt. With a full cab of passengers, the speed slightly dropped off, but only by a few mph.