So this morning I started up blazer. While I was cranking it over just before it started it sounded like it backfired out the carb. Now all the sudden it's idling higher than normal. I'm not totally sure but I might be hearing a vacuum leak in the dash. Other than a vacuum leak what could have caused the idle to jump suddenly?

Edit to my last post...... Didn't see the obvious until a day later. The pcv hose coming off the throttle body popped off from the backfire because or was all cracked and old. Replaced the hose and pcv and seems to be running as it did before. One question would be though, what would be causing the backfire? I have had it do that a couple times before but rarely. Also, a few times it's hesitated a bit when taking off from a stop but otherwise seems to run relatively smooth. It does idle a like rough but nothing more than feeling it a little while you're sitting at a light. haven't checked fuel pressure since I don't have the fittings at this point. Possibly the iac having issues? Not exactly sure how to test that.