Yeah the balance of the kart without the wing will defiantly change. I have the black laydown F-125 with the big wing. I have run with and than taken it off for sessions and the balance changes quite a bit. It has always been drivable but defiantly a little tail happy. Do you have a diffuser on the kart? That helps quite a bit to minimize the balance shift and like Sam mentioned shifting some weight to the back will help too. But for sure taking a little downforce of the front will be the biggest help to balance it though.
If you do it defiantly post results. Daytona is the one track I think removing the rear wing might be a help. Everywhere else I have always gone faster with the wing. Even at MIS this past weekend I ran without the wing and while I went 4 mph faster on the straight but 2.5 secs slower per lap. Now they only use 1/3 of the oval there instead of 3/4 of the oval like Daytona. I would bring all the parts to put it back on and do a comparison if you can.
Is 145 the fastest mph you have gone there? Or the fastest a superkart has gone? I thought lay down 250s have hot 160mph so just curious what the number is.