In need of 81 xs400 idle/running issue help

[Goldberg2363]

Hi i'm new to the forum so i'll introduce myself real quick. A few months ago i bought my first bike a 81 xs400 and am slowly working all the kinks out so i can start turning it into a cafe racer. Well as i soon discovered after buying my xs400 they all seem to have idle problems. I finally seemed to have mine worked out and just had to blip the throttle here and there then all of a sudden it started cutting out after sitting at a light. It would be idling good and then i would notice start to slow down so i give the throttle a little blip and it immediately shuts off and then it takes FOREVER to get started again and i usually end up having to get off and push it off the road and get it started again. I've gotten it to where i can duplicate it and it seems to be only after sitting at idle for about a min and then trying to give it some gas. The other strange part about it is if i get stuck in traffic and it cuts out on me and then i get it started again and go a few miles without having to stop its fine again. I'm almost positive its the petcock and that its not pulling enough fuel at idle to keep it going. So after all that i'll get to my questions. First does this sound like a petcock issue? and second my petcock is the vacuum kind and i wanted to know if i can replace it with a non vacuum petcock like one on mikes xs? and if so do i just put a blind plug on the carb holder that has the vacuum line going to it now? Thanks for any help anyone can give me.