Rough idle, wont do more than 40mph.

Rough idle, wont do more than 40mph.

2005 GMC Yukon 1500 truck runs like it has a few dead cylinders and won't do more than 40mph. When it gets to normal operating temperature it gets worse and quickly dies and doesn't want to crank again until engine has cooled off completely. Just put on new coils, wires, and plugs and the problem is still there please help!