I have a 2007 Polaris Ranger 700 EFI. The unit starts fine, accelerates and all is good. The problem is under light throttle cruising at 25mph to 32 mph the bike surges. I have replaced the air filter, cleaned the map sensor, changed the spark plugs which were black as the same with tail pipe. I changed the TPS with new OEM, set voltage at .70. My fuel pressure is 42 psi. Unit has all kinds of power and idles just fine. What am I missing?