[bnoon]

I would start by rotating the choke coil just a little more to the closed position. Since you stated that you have to feather it until warm, means too much air is getting in under choke situations. If the high idle RPM is OK, leave that alone, but you may have to adjust it after closing the choke more just FYI. On my 454 Quadrajet, the choke is completely closed on a totally cold start, no 1/4 inch gap.