1998 4 by4 runs good till you floor it ,it just falls on its face, pops,wont go let off under 2000 rpms runs fine please help.

CK FOR VACUUN LEAKS

After 14 years I think it would be reasonable to have bad catalytic converter. Is there some reason your not accepting this?

white smoke can be water in the exhaust if you park with the rear end facing up hill it will store water in the cat and take a few miles to clean out. 2000 rpms is a bit fast. should be around 800-900 rpms. it could be a sticking idle control. take it off and give it a good clean out.

check the firing order as it indicates 2 wires crossed

This is pretty simple, pop your hood open and look on the left side
with the car is running turn the screw counter clock wise till your rpms reach the 1 mark you will find the screw located in the same metal bar as the foot pedal cable...still cant find it ? pop the hood open and tap the gas pedal till you see the pedal move the cable line to carburetor under your hood it is right above the alternator.

Sometimes the screw gets messed up and you will have to replace the whole screw and crew housing this happens when it sticks there is also a pin that is under the circle wheel part of the idler.

is your car still running on carburetor engine? if yes, have your carburetor cleaned. while cleaning, replace the secondary jet in your carb. the normal primary/secondary jet for a 1.6cc engine is 105/135.

could have a bad pressure regulator pinch off return line to see if it inproves if not prob coil cover againe very pop prob.

The first thing to check is the fluid level in the transmission. If quite low, look for red leakage on the floor where you park. Suggest you find a quality auto transmission shop to check this out before you require very expensive service. Good luck!

Timing belt broke??

run engine codes, had same issue once before it was bad computer good luck