Odd engine surge
 

I have done some searching, but didn't really get anywhere with it, so I am tossing it out to you good folk for recommended solutions. My engine is surging, but only when there is NO load on it. Sitting at a stop sign the engine is pulling against the brakes and idles just fine. Any kind of acceleration or cruise is fine. But coasting down a hill or to a stop sign, it is like the tach needle is "bouncing off the floor" or like I am giving the throttle a slight bump to keep the idle from going to low, until I am slow enough for the brakes to make the engine work a little. It is only about 200-300 RPM worth.

For example, if I'm at 1500 and then take my foot off the accelerator the tach drops to 1300 ish, bounces back up 1400 ish, down to 1100-1200 back up to 1400 down to 1000 back up to 1200 ish etc etc. It is not just the tach, that is just my visual, you can hear the engine reving like your hitting the throttle when it hits a lower RPM. If I hit the brakes, it goes away, because braking is loading the engine to a certain extent.

Some threads have suggested air in the lines, but in my thinking that would give you an RPM dip vs an RPM bump as it is coasting down. So I am at a loss. Any thoughts out there?