Good point, since temperature seems to be a factor, I'd be looking more at the MAF instead, not sure if they looked at temperature as well on a stock 08, but cooler temps have denser air which will be a factor.
Part 5 of the link I sent has the procedures for the MAF, Ford Mustang MAF - Solving your idle problems
Even though this is a prior generation from your pony, the basic procedure still applies.
Temperature (due to expansion and contraction) could be causing something in the throttle body to become a little sticky which might also cause improper changes in control until you've opened up on the throttle more. Without the ability to monitor everything that's actually happening while you drive, it's difficult to pinpoint exactly what's giving you the bug. The best thing in this case is to bring everything in the throttle body back to it's best working condition, then sort out what's left. The only other thing that mey cause a surge would be a vacuum leak, but that's usually just at idle, but since this occurs just at very low throttle, I'd stick that thought on the back burner, but not throw it out entirely.
Could you clarify something? Is this an 08 with 12K total miles or is that all you've put on it?