Sometimes wont crank, wont go over 2.5K... and check engine light broke

I've got a 92 T4R 3.0 4x4. I actually just bought this thing and within the week it started having problems. Sometimes i would get into it and the motor would turn over but it wouldnt even crank. then other days it would start just fine and run for a bit. changed the fuel line filter, plugs and wire and distrib. ran seafoam threw it. but still it has trouble starting, when it does start a plume of white smoke comes out exhaust. When its around 2500 RPM it hits a wall and wont accelerate... So i am at a loss here, Anybody got any ideas?

 

sounds like the makings of a rod knock, mine did the same, and you could barely hear the knock. but thats exactly what it was, how`s your oil pressure