727 doesn't shift into second gear like it should

My question is that in the instructions it says to install the small plug with the hole in it in the front clutch apply hole on the trans where the valvebody goes. Should I use this also? And what does it do? Is the plug for the band overlap remedy or for other reasons.

Just for a reminder I am still using the B&M kit in the valvebody.

I answered via pm but I'll answer here too. That cup plug is to eliminate 2-3 shift overlap. I think B&M kits also use it so your trans. may already have it installed. If it was shifting good from 2nd to 3rd I'd leave it as is.