2009 D13 idle problem loss power,ishif issue need help pls

hi there,I bought a 2009 780 832km with d13 less then 1 month ago,when parked and idle with the cruise control the rpm goes up and down between 650-720rpm aprox,even the engine sounds like pounding , after couple min is back to normal rpm and so the engine noise . I was on my first trip to montreal when got the regen request on my dash ,on my way back was already flashing ,I took it back to the dealer the found a code mid 128 ppid 79? fmi 7 or something like this, they sad was electric issue with the 7th injector they fix it no charge . On my second trip to WI with like 42,000 pounds load the engine seems to have not enough power is like pounding again ,after getting the speed runs ok ,and also got some kind of vibration-grinding around 50-55 mile only coming from my Ishift trany and not all the time.so I took it back into the shop they found play in my output yoke coming from the ishift and when they move the yoke like something move inside my trany too,they sad it is normal play and make me to change my drives air bags leveling valve cause I lost air in my bags in short period of time when stoped.Hope is not my transm. did not get a chance to try with a loaded trailer, tomorrow I will.about the power loss the pulled my valve cover to check my injectors they sad I have cronical injectors and likely steel inj.cups also but found the inj.harness cracked in 2-3 places.I got lots of questions here but if someone willing to give me some good advice that would help me a lot not going bankrupt.i appreciate .