No it wasn't the installation. I though maybe after first time.
But after the attention to detail 2nd time I ruled that out.
The material the 2912 is made of is a better quality and the lip is stiffer.
I also don't like band aids in situations as this especially.
If a low vac sb can run without special attention with no leak then this L48
should. GM was able to do. It boils down in my opinion again to quality of materials.