No offense just poken you a bit.
they did not come 33". are the 12.5 wide? if so they are after market.
3.8's are very picky on gears. Jeep should have never used 3:21 gears. those that did get them came with like 29-30"s? and they are street tires. Most people end up with 4:88/5:13 for 33/35". 3.8 is well known to be lacking in torque. Off road it does ok but that is by gear reduction.
if you have 33"s then that is thetrouble. Need a regear. That will help the MPG, alittle.
It helps to fill out the INFO page on the Jeep in your profile.