2000 silverado 2500 6.0l no power no wot shift with U7198.

[BigDawg]

I'm using a U7198 with latest update (9r17). With 87 octane tune installed truck has no power say 50% less than stock. With Diablo tune installed part throttle say to 50% is shifts fine but under wot it does not rev pass 3500rpm and refuses to shift without backing off the throttle 25% or so. Once throttle is reduced it will rev to 5000rpm but surges with occational backfire and power sucks. I have tried without modifying the tune as well as reducing spark timing and increasing fuel slope but nothing seams to change. Truck has a freeflow custom exhaust as well as a volant cai. When I return it to stock tune it performs well as usual. I pull a travel trailer and was actually seeking improved mpg with this purchase. Any advise before I return this pos to the place I bought it from?

[mikel]

never seen this before, I wonder if the stock tune is not 'stock'.

Can you post a copy of the stock tune here?

Thanks

[GMC1500HD]

this sounds alot like what mine is doing