I've been having surging at light throttle. I was also getting bad gas mileage(running rich). Found out I had an exhaust leak right next to my O2's on my Pacesetter LT's. O2's were seeing extra oxygen and it caused the car to run poorly and surge at light throttle. Now even with my medium sized cam I have no cam surge.

Just thought I would post this because I've seen a ton of posts on here that describe pretty much the same problem. Oh by the way I picked up 3 mpg.

 

Good info for people with headers.

 

I believe that the most common problem is vacuum leaks. There are plenty of opportunities for split hoses and poor connections.

I had symptoms of surging, stalling, poor mileage, DTCs, and lousy performance...all due to a leaks in the intake system, at one location or another.

The visual inspection is always the most important.

The other day, at a friend's house, his girlfriend was whining about her Thunderbird, when she described the problem, I immediately called out a vacuum leak as the problem. Sure enough, when we opened the hood, it had a hose flopping around and the intake clamp was loose to the throttle body. Tightened everything up and the car purred.

Always use the visual inspection first and follow/trace each line from start to end. Tug on lines and look and/or feel for cracks and other defects. Hoses are about the cheapest of repairs you can possibly make.