I have an 09' International 4400 Durastar with the Maxxforce 9 motor that i recently purchased. The truck had the emissions removed before it was purchased. The truck will stutter, backfire once and puff black smoke intermittently at around 1800-2200 rpm and doesn't act like it wants to pull anymore after this. The overhead is being ran and checked on the truck currently. Any Ideas as to why its doing this? VIN is 1HSMKAZN49H143037.