[Gene563]

Well, I had the scoot running well and made some more adjustments. I thought the plug seemed a bit light (not blistered) and thought it might be good to up-jet. I opened up the stock air box a little more and stepped up to a 115 main and 38 idle jets.
On test ride it seemed to surge at speed and would stumble off idle . I swapped back the 35 idle jet and since then have been having issues. I seems like I have a vacuum leak, but I have tried all I can think of.
What it's doing ... with the opened airbox, accelerating you hear "Bwaaaaaaaa", at certain speeds and even hard acceleration from stop it will change, more like "BwaaaaaAAAAAAAA" along with what sounds like a hissing noise and power loss.
So far I have reduced the main jet back to a 110 and taped up some of the airbox holes. Swapped out the carb with a spare, same size, same size jets. Vacuum line, verified/adjusted the valves, removed and inspected the intake (ordered a new one and gasket). I'm going to swap back the original carb once I get the new intake as the replacement seems more difficult to set the idle mixture.

I'm sorry for the long post, but I'm getting frustrated. I was wondering if the CDI could cause this, but it would be intermittent as at moderate throttle it runs ok. Spark was good when tested today.
Any ideas would be much appreciated.

Thanks, Gene