3rd gear bogging

[Zach079xxx]

1985 350 Holley 600 carb weiand intake that I just had built and a turbo 350 also built about 2 months ago. Truck ran like a top then I left a buddies house late about 11 PM it was chilly about 55-60 degrees here in VA. First was fine, second fine, third I noticed a problem. It started to bog down, hardly any power. Stomp on it it shifts to 2nd then back to third bogging. I figured it was the cold but it's still acting up 2 days later. What gives? Why is it doing this? I can manually shift it and 1-2 are great then 3rd its ridiculous. I don't know much but if you can point me in the right direction I can figure it out. There's a show Saturday that I'm going to so I wanna have it fixed. I'm taking it to the guy who did all my work if I can't figure this out. I sunk over 3 grand in it and now I'm getting a little angry