24 Valve Cummins Excursion, mid range power problems!
 

I bought an 01 Excursion that had a 5.4 in it and replaced the motor with an 01 24 valve. I purchased the conversion kit from Diesel Conversions out of Montana. I have the motor hooked to my 4R100 transmission, and remapped the tranny with an Optishift programmer. In 1-3 gears, the bottom end power is excellent, but at about 70-80% throttle, the motor bogs before it shifts gears. Once I hit overdrive, the truck runs great. Any input on what the problem might be? Could lowering the shift points be a fix? Any help would be greatly appreciated. Thanks.