Need some help 81 KZ750-4LTD

When I start up the bike and let it warm up, I cannot fully open(about 3/4 open) the choke. At low end i get some popping from the intake and when i accelerate and then release the throttle the engine revs up to 3-4k rpm and slowly backs down to idle after about 5-6 seconds. The slides are free, the pilot jets are clean.
What are some things to look for?
Thanks

I had a similar problem with my kz650-H1.. from previous posts on here I determined it was a vaccum leak behind the rubber mounts for the carbs... spray a little carb cleaner at those rubber mounts and see if the idle changes are becomes erratic it may even stall... just my two cents

Exactly what it was. Thanks for the help. I runs great now.