1994 Toyota Supra Smog/idle issue

I have a 94 Supra TT. I have a couple problems with the car. It won't pass smog. I had a new catalytic converter put in and it barely passed last year and now the cc is ruined. I have a wideband FJO A/F sensor and I'm usually in the 12.5-13.5 area. The car idles weird. It stays at about 800 for 2 secs then drops to 600 for 1/2 a sec then back up to 800. Also, if I have the a/c on and I push in the clutch the idle drops so low that the car stalls. (I've noticed that in the morning when it's not so hot that this doesn't happen. I don't know if that is coincidental or not, but it never happens in the morning.) The car only use to stall with the a/c- so I left it off- but now it has stalled a couple times just randomly. Any ideas?