Toyota Repair: Engine Knock, piston slap, manual tranny

Question
I have a 2000 Toyota Tacoma with the 2rz-fe engine and 5 speed manual tranny with 58000.  Here's my problem, After the engine warms up when I start in first gear my engine starts knocking pretty loudly until about 2500 rpm and then goes away I can't hear it in 2nd or higher. At idle with the clutch disengaged I still have the knock but it is not as loud. I have heard from a lot of other toyota owners that they had a knock problem too but it was at startup and went away when the engine warmed up. I don't know if this is helpful but I do have a shimmy at speeds in excess of 60 mph but I figured it was suspension or tires and was going to take the truck in to have it looked at.  Any ideas on what to check for would be helpful. I have heard knocks before but they were usually the valvetrain was loose or pinging. Again there are no unusual noises when I first start the truck in the morning and drive to work, they start after it gets up to temp

Answer
I would guess its not "pinging" if it does it at idle.
Could be piston slap or a bad wrist pin.

Strange that its not in any gaer but first. Could be a trans or clutch problem,
Are you sure its in the engine?

Tough for me as I cant actually hear it.

Mike