GM is killing me with these master cylinders, they have low stock of them and they all come from michigan.
I've Done all I can with my master cylinder, i cant modify it any further. over the weekend we've got it to flow as much as it can. I tried it in my car again this morning on my way back from the chevy dealer (had to drop off the bad master cylinder that doesnt hold pressure) My car does not grind anymore at high rpm shifting.
I'll have a new master cylinder tomorrow so i'm looking for someone near me to test it on sometime later in the week or this weekend.