We are really far away from a diagnosis.
#1 - Pull codes. Search the site on how to do this, it is the same as the 5 liter cars.
#2 - Report back. At this point, it could be literally anything...
Worn spark plugs, failing ignition coils, failing ignition module, weak fuel pump, clogged fuel filter, bad fuel injectors, bad MAF, contaminated fuel, plugged exhaust/clogged catalytic converter, ECM...