engine boggs down while accelerating

[gemini]

I have a 2006 GZ250 with 8,000 miles. I just had it tuned up less than a month ago. I was riding home from work the other day, everything was fine, then I stop at a red light. When I accelerated the engine bogged down. I got out of the throttle and it idled fine. I tried to accelerate and it would lose power again. I coasted into a parking lot. I shut off the bike and it started right back up no problem. The bike idled fine but I could not give it much throttle without it bogging down. I left the bike for a couple of hours till traffic slowed down. I went back and it started up just fine and was idling normal but still it would fall on it's face when I tried to give it throttle. I put it in 1st gear and was able to idle around the parking lot fine. I was able to shift into 2nd gear and could give it just a little throttle before it would lose power again. I finally was able to ride the two blocks home but if I gave it throttle and held it open the bike would bog down for a second then it would surge back to power for a second then bog down again. It jerked up and down all the way home as long as I was trying to accelerate. I started it the next day and it did the same thing. I rode it around the parking load I could ride in 1st giving it just a little throttle before started bogging down again. I have tried riding it a couple of time now and it runs fine as long as I only give it a little throttle. I can keep speed and shift up to 2 and 3rd gear giving it a little gas. Once I get to a certain point it starts jerking again. Any Ideal what is causing this.