1996 Jeep Grand Cherokee

Hi, I have a grand cherokee and I have a problem, most likely caused by me. Earlier today, I took my throttle body to my friend who owns a machine shop to have the bottom end bored out. He shaved 4 millimeters out and we put the butterfly back in, and after I re-assembled the throttle body. I disassembled the battery connections to reset the computer and connected it back after a few minutes. I put it back on, and reinstalled all of the wires and started it. First, I got a check engine light, then it idled at 250rpm than after I revved it a few times, the rpms hit 1500. Than I drove it on city streets, and it was hovering around 500rpms. I got to my driveway and put it in park and without touching the gas, it hit 1500rpms through park, reverse, and neutral. If I put it in drive, 2, or 1, its perfectly fine. Any ideas? (I probably screwed myself over just to get a little bit more horsepower out of my tired 4.0l) ive replaced rotor, distributor cap, spark plugs and the wires, and I think the air to fuel ratio is fine, but I could be wrong.