Hi Tracy, I am guessing that my 98 Cherokee 4L will be similar and the 98 2.5 L Wrangler that I was working on looked identical, which leads me to my question or observation:
On the 2.5 L, the TB to manifold gasket inside diameter was wider than the inside diameter of the TB bore diameter. I don't have the exact measurements here, but the difference was close to 3/8 to 1/2 inch difference overall, or close to 3/16 to 1/4 inch when centred. I closed off the IAC opening, bored 2 holes on each side of the original site of the opening, and then cut a channel on both sides. On my first cut, I did not take into account the gasket size, assuming that it was the full width of the TB base, which it wasn't. If I left it like this, the by-pass airflow would have exited into the manifold at the first edge where the channel would not have been covered, or right into the zone where the groove was cut. The IAC would have worked as per normal, but would have been interfering with the potential improvements of the groove and I would have not accomplished a thing.
I noticed this when putting on the gasket, so I filled the the channels, marked where the gasket actually sat and re-cut accordingly. The gasket itself is quite narrow and so didn't allow very much room for error. I used a 1/4 inch diam. cutter, but should have gone narrower, as I only had at some points, a 1/16" contact surface for the gasket to seal. I put it on and did have some vacuum problems. I took it off one more time and ended up cutting a 4x4" by 1/4" aluminum plate, cut a hole 1 7/8" diam (same size as the TB bore), made a full plate size gasket for between the TB and plate, and the original gasket between the plate and the manifold to compensate for my wider than adequate channels. I did have to adjust the cables (trans and throttle) so the rpm shift points were not out of whack. I know wouldn't have had to go to this extent if I had a very accurate cut between the prescribed areas of the gasket sealing area and of course checked where the gasket laid from the beginning. The surface area of the intake mating surface is raised and offers very little overlap for just a larger diam. gasket: thus the plate.
On your jeep, I see that you cut the channels very close to the inside diam edge of the bore. You must have had a wider gasket, as the gasket I had on my jeep I think would have not covered the channels.
Let me know how that worked for you.
Again, I will send pictures on the 2.5L jeep when I re-cut the groove after it gets back home.
Best regards,
Luke