Two things need to be done. One is a compression test. Secondly is a vacuum gage reading if you can get it to idle. Personally, its either a head gasket or bad AFM. When the AFM goes bad, they tend to run extremely rich known as the limp home mode. As suggested, check the AFM door to make sure it swings freely. If the smoke is white at start and lots of condensate dripping out the pipe, its the head gasket. Blue smoke and fuel smell is a fuel related problem. Black oil smell smoke is bad rings and burning oil.

Hope this helps.

 

Vrey important to have the TPS adjusted correctly.

http://www.4crawler.com/4x4/CheapTricks/TPS/index.shtml