Miss under loae

[vwhit]

I have a 1994 Chev. Suburban 2500 6.5 turbo diesel I recently purchase with trans problems. I had trans rebuilt approx 2k ago. I have notice a once and awhile skip underload change to 2nd and 3rd then clears up. I talked with the previous own that told me it has done it since new. She said it has had several diagnostic test and the IP and lifter pump replaced several times by GM dealer, but after awhile the skip would return. She said no has been able to correct the skip. I check code and got #68 trans slip and 78 wastegate solenoid fault. I also opened the drain and the engine shuts down very quick. This electronic stuff is baffling to me. Can any one help. Thanks!