these are the things to have your new dealer do first. compression and a leak down test. you can have good compression but have a ring sealing issue? this cause's poor idling and erratic peak rpm's.
tps has to be set right. meaning the base voltage with the throttle cable unhooked, idle screw backed out, and the throttle plates fully closed, has to be .700 vdc. if not the tps sensor has to be moved to obtain this. then the idle screw turned in to reach your idle spec voltage for your sled. then a slow sweep check both throttle wo and back to idle position. a couple of times.
throttle lever free play of .015-.030 or the thickness of a credit card has to be set.
throttle safety switch should be replaced or tested.
pull the recoil. the air gap at the crank position sensor and the trigger coil has to be checked. .020 air gap. this being off the sled will die going into reverse and cause erratic idle.
wiring above the throttle body's , and al connectors there and at the ecu etc. should be inspected closely if non of the above changes any thing?
stator out put needs to be checked. the d-wrench won't tell you the stator is bad. key codes are low voltage to the fuel injectors, low battery voltage, etc.
if this all checks out then replace the injectors. all of this if the reeds are for sure new.
a bad ex. temp sensor does not cause erratic idling. a bad water temp sensor does not cause erratic idling, a bad t-map sensor could? but not usually.
good luck. I love problems like this. never been beat yet. there is something wrong? it takes a relentless checking of everthing systematically.