Does the PT2 have proper airflow when its removed from the mod? If not remove the head(coil) and reinstall it (or install a spare) and see if the draw is effected. Sometimes the installation of the heads/the heads themselves can effect the draw.
If the draw is decent with the tank disconnected, you may have to attack it a different way. Did your PT2 came with the conical beauty ring? (hopefully)
Start by tightening the tank on the Vamo just till the point it will fire (dont tighten down), test the draw/air-flow with the tank loose. If you've got airflow, you can use the beauty ring to solve your problem.
Remove the tank, install the beauty ring (wide side up) on the vamo's ego threads, screw the ring up until it is approximately where the base of the tank is when attached to have a draw(may take a few adjustments).
Once you get the ring set to the proper height, you should be able to screw the tank on, and it will seat against the ring giving it stability/support, while also keeping it higher in the Vamos 510 to help with airflow.
It will also help fill the gap between the tank and the vamo.
View attachment 282731
View attachment 282733