All of the diagrams of Pentair 2 speed pumps that I see have a drain plug. They are normally located in the bottom of where the water comes into the pump (the place you empty the basket from).

As far as the vacuum hose, all of the ones Ive seen have 2 different ends (usually different color too). One of them swivels and the other doesnt. That is in addition to the swivel connection on the vac head itself.

How many bubbles are you seeing thru the return? Can you hear air in your multiport valve? (will sound like a crackling noise). Try taking a length of garden hose and put one end on each pipe and the other to your ear. Try the inlet to the pump, then from the pump to the filter. If there is air you'll hear the crackling. If there is no air in the inlet (possibly more than one inlet to try depending on your pipe setup) but the air shows up from the pump to filter, you've narrowed it down to something in the pump. Thats actually how I started to narrow down my suction leak. Even the little drain plug leak was pushing a decent amount of air into the pool.

-Chris