Rpm goes way up and way down
 

Ok so ive been dealing with injector issues and tryck finally was runing good but on start up only if its sitn overnite or when im at work for 8-10 hours. When i start it it will shoot out a puff of greyish colored smoke then about 5 seconds later the rpms will bounce up and down and sometimes actually bounce so low it will stall out.its a 2005 f250 6.0l with about 170000 miles. It will bounce for about 2-3minutes and if it stays runing then it smooths out and runs like a new truck. In the last month ive replaced 2injectors thermostat oil filter fuel filters oil a couple diffrent sensors. Wasnt sure if anybody else has expierianced this type of problem.