2002 explorer suddenly won`t pull

Sounds as if your catalytic converters are plugged up. It's not a cheap repair, if you do it right. You have to replace the 'H' pipe, which contains the converters. That pipe may set you back 5 or 6 hundred bucks!
An emergency fix (though not legal) is to remove the existing pipe and with a long steel rod, bust out the guts of the converters. You have to shake out the contents after you bust them up so it's necessary to have the pipe off the car.
If you want to test and make sure that this is the problem, you can disconect the pipes from the exhaust pipes coming down from the engine without removing them from the car. Start the engine and try to rev it up, without the converters connected. If it revs like a 'racecar', you have probably found your problem. Good luck! Dave