Removing the front bumper on a 90-93 teg is a 10 minute affair. 15 minutes if you're by yourself, lol. I've done it a million times.
to remove, simply remove the front bumper turn signals (2 screws for your 90-91 signals)
remove the 12mm bolts that hold it to the support (these will be found behind the turn signals) *2 on each side*
remove 2 screws at the rear of the bumper in the fender-well. turning the wheels inward helps alot.
remove bumper
****NOTE**** if the bumper has NEVER BEEN REMOVED BEFORE, EVER. there might be a few 10mm bolts underneath holding the plastic splash guard in place. there are only 4-6 of them. they are in a straight line, and easy to remove. unless you're anal about details, i wouldn't even put them back in. i didn't and haven't had a problem ever. and i have less than 2" ground clearance.
while you've got that bumper off, remove the stock intake resonator as well. if your intake system is stock, this will make it sound a little more like a short ram intake. a little louder, but keeping that nice and stock look. this is also VERY EASY to do.
I removed my bumper, took out the stock resonator and all the little other air ducts attached to it, installed a cold-air intake and re-installed the bumper in less than 40 minutes.
best of luck to ya