Moped Army

I've been breaking in my new metrakit 80 big port w/ 19 PHBG the past few weeks (well, it's basically broken in now) and now that it's approaching the 'safe zone' of break in, I'm starting to open it up a bit more. When I do so, I've been having this strange sudden and short lasting bogging when letting it rip. At first, I thought it was soft siezing briefly, but I've started feeling like it's something more fuel related.

After about ten seconds after gunning the engine (somewhere in the 35-40 mph range) the engine will suddenly stall out for a moment and feels like it lags a little bit. It almost feels like a soft seize, but as soon as I ease off the throttle a bit, it runs beautifully.

I'm basically just looking for some ideas. Everything seems leak free, and I'm running an 88 jet, needle all the way up, and an estoril pipe w/ restriction still in.