Won't shift
 

I have a ls1 with a 4L60E automatic it's not wanting to shift under acceleration, it shifts fine just driving around. Fluid is good. The only thing I found was a fitting on right side with nothing on it. Is this a vacu
um fitting it's in middle of pic. Thinks for any help.
https://cimg4.ibsrv.net/gimg/ls1tech...ac1b5829dd.jpg

Looks like a vacuum connector, but there are no vacuum connectors on a 4l60e, so it's probably to something else. Looks like one for the HVAC in a Camaro though.

That plastic might be a check valve for the transmission breather line. Check and clean the MAF sensor