I had the HKS R-type FMIC fitted back in July 2003 and on the way home from CW's my Air con cooling power was very much reduced....or you could say it was not there at all
I thought that the cause was the FMIC was blocking the air flow and heating up the air that did get through to the Aircon rad but, the FMIC was only part of the problem.
Since getting the car back the AirCon is as strong as ever, I have had a new rad, a new Aircon rad, it re-gassed and the FMIC put back on and it works A1 now
So, my thoughts are that the FMIC install only highlighted that the Aircon rad was on it's way out or maybe it just needed re-gassing ??
IMO I'd say that it was the Aircon rad that was duff as most of the other coolers were on their way too (SMIC, Diff Oil cooler, normal rad etc....) but, wat confirms this too me is that the ride up to CW's the AC was fine so, that's what I think anyway.
So, if you get a FMIC and the AC goes duff then, don't blame the FMIC it could be that the rad is on it's way out.
My rad was 8yrs old so, well ready to be replaced I guess.
HTH