Goose

Ok, so I've been trying to sell my truck for months but I've had 15 no shows and people who just don't now reply and it getting frustrating. I have an 04 and it runs rough at idle when it's cold, when the engine is warm it won't idle, just dies. Zero power at WOT, like 0. Going from 80kmh-100kmh at full throttle took a legit 2 minutes. I've basically narrowed it down to the Phasers. Now, if I decide to fix it what's the best route, the lockout kit? Or just fix it back to stock again. Also what years of 5.4 will be able to drop into my truck without having to put different computers and such in. (I know I'll have to take the computer from the donor truck, I'm just curious about it running the gauges and everything else.)