Strange shifting issue

[Daikorian]

So. Recently had to have my transmission replaced, the whole transcooler/radiator failure thing, and now it's got a strange thing going on. Best way I can explain it, is that when I am in manual shift mode, it's a 4 speed on an '04 XR6 Turbo, whenever I let off the gas or downshift, it seems to drop into a coasting mode. There's no engine braking, and even if I downshift to first at higher speeds, there's zero response until I start giving it gas again. When I do give it gas again, it'll rev up to around where it should be at that speed before engaging again. It seems to work better when in automatic, and seems to upshift just fine in manual, it's just that downshifting or letting off the gas causes it to coast. It seems more like an electrical issue of some sort, but I've got no idea. Anyone have any experience with this, or ideas of what it could be? Thanks!