89 XJ - HELP! Engine is choking...?

[YellowXJ89]

I have 89 XJ with 240kmi and it had been working great until now. The truck started to choke @ 1600-2200rpm from dead stop every time. It didn't die on me though... :o) I though about bad fuel in it first and put premium in, but no change. Finally I got some time to change the spark plugs (they were all white except one), IGN wire set (two of them broke off at plug) and air filter. I also checked on distributor cap and one of them had some rust on it. So I cleaned that out with sand paper. It's been a couple of days and doing better but it still does once in a while. Any ideas with what's wrong with it?

I also noticed (not sure if it's related or not) that FULL TIME 4WD light starting to come on very randomly. Maybe there is a vacuum leak somewhere...?