I'd almost bet my life that the puck is not sealing against the hole in the elbow. I had the very same problem with no boost off the line then low boost - 13-15. But mine was only occasional. Worse, it usually did a great burnout easily then would stick slightly open at the line. One time when attempting to crank up the boost I was trying to get the actuator rod back on the wg arm and I felt it "click" and snap shut. It only moved about a millimeter. Barely enough to see. But right there in the pits I took the elbow off and filed the edge of the puck and the edge of its hole just ever so slightly until I could close it easily every time. Never had a problem since. HTH
And if you grenade your trans be sure to flush your converter VERY well before you put it into your fresh new trans. There's a whole 'nother story there but I prefer not to get into it.
And if you grenade your trans be sure to flush your converter VERY well before you put it into your fresh new trans. There's a whole 'nother story there but I prefer not to get into it.