Hey mate, im only grasping as straws at the moment due to my lack of experience but my investigations lead me to transmission issues, internals (1-2 accumulator modified to have NO spring) and a modified transgo plate...
The vss error only kicks on on 1-2 upshift at vss reading of 55... But I'm WOT so forced change is supposed to be 64km/h..
When I'm not driving it like I stole it lol it's actually going pretty well
Still will get a wideband kit, but more importantly I plan to get trans back to stock ASAP...