Haha, no worries...The rest of the SK4L60E is fine as it does contain some useful corrective parts. Just put the electronic pressure control (EPC) over-pressure relief mod in the trash. Transgo designed it as a safeguard to dump excessive line pressure if/when the EPC itself fails...The EPC is basically a 'stop-down' for pressure so you're not running full/max line pressure at part throttle...If that happens, shifts become brutal to dangerous and parts inside the case, as well as the case itself, can break. But you can head that off by simply replacing the EPC solenoid at the proper service interval (think its every 100k or so).
Beyond that, 4L80Es are known for having worn actuator feed limit valve/valve bores that can result in insufficient apply oil being provided to the shift solenoids and EPC. If you start inexplicably slipping in gears, especially 3rd and 4th after VB replacement, I'd suspect the AFL valve (or TCC regulator valve - it's prone to wear also).
