I have a 86 GT, 5spd. Engine is a 5.0(302) with gt40 heads and intake. e303 cam and shorty headers with catless xpipe. I am running microsquirt from efisource and an aem xseries wideband. Engine starts and runs great up to operating temp. I have an electric fan that's controlled by the ecu and works great. Maintains 195 degrees without error. The engine will idle around 1000 rpms and when it starts to idle down it starts surging and will swing from 300 rpm to 1500 rpm and will eventually stall. Ive tried messing with timing and fuel tables. Ive messed with iac frequency and other misc settings and can not for the life of me find the issue. Ive attached the tune file. Thanks in advance.