Had a head gaskets and head done on my 5.7 liter v-8--before was running fine just smoking from the anti-freeze in exhaust. Just a little rough idle. Got back and ran good 1/2 day and then ended up with rougher idle then before. All smoking gone, but the rough idle has went from rough idle to jerking gone down the road and to me seems to be running rich. I know when you take them a part sometimes you get trash in the system. Ran a tank through and did not improve. Diagnoses --fuel pressure/fuel injector/ fuel filter(replaced)-mech says he sees a problem with cyl 3-8 not fire but he beleives injectors? Seem right--and is this just luck of the draw after work being done in the area?