Actually, yes.
T4 open hole inlet flange measures 2.938" L x 2.000" H on the inside diameter of the flange. Outside diameter is 4.250" L x 3.750" H.
"T6" or actually the T5 inlet flange measures 3.480" L x 2.380" H on the inside diameter of the flange. Outside diameter is 5.313" L x 3.625" H.
Garrett called this flange a T5 flange in the beginning, and I believe T-netics followed suit by calling theirs a T6 flange. But generally , T5 = T6 when it comes to inlet flange comparison.
Hope this helps.
Patrick