Ok I know this isn't exactly a third gen but it's beyond me.

I picked up a truck pretty cheap because it was ran in a mud bog and it somehow reversed vacuume and sucked mud into the motor. I've flushed the motor and to my knowledge it's all out.
It fires up and idles fine, but under load (up hills or brake stands) it will miss and lose all power. I've cleaned the mass air flow, intake and replaced the cap, rotor, and plugs. (I'll be replacing the wires this weekend).

I'm starting to think its the timing chain, would that affect it only under load or even at idle? Any ideas guys? It's really starting to annoy me.