Yes it's a night and day difference when you tape over the hole. I recently got my T2 and was very underwhelmed by the sound initially. Very anaemic/thin sounding due to the complete lack of bass. Though sub bass was there, just nothing above it. Made for a very unsatisfying and unbalanced listen. I'm not a basshead by any means but putting some micropore tape over the hole made an enormous difference. They really do sound great now. If I hadn't read up on the T2 after buying them and seeing the talk about the bass mod then I'd've probably put them away in a draw and never used them again. Quite why they're tuned to be so anaemic I don't know.
Although doing the micropore mod will increase midbass bleed, make the sound warmer, and loosing a little of the soundstage. also taping the vent somehow making it more fatiguing to listen, i don't know why.
I prefer not taping them nowadays