Truck is missing really bad. I changed the plugs and coil packs and seems to gave gotten worse. I hear a whistle sound when accelerating under a load, not in neutral. it is a 2008 ford f150 5.4 triton...

 

Welcome! What plugs, coil packs and are there any codes?

 

Somebody might be able to chime in, but there are better places to ask this question. There's a mechanical section or you could ask it in the 2004 - 2008 section. You're in the 2015 - present section. You might also be able to do a search for the same problem. (almost sounds like a vacuum leak to me) :-)

Good luck