Should I lose power when the intake gasket goes bad?

I own a 2000 Pontiac Grand Am, 3400 V-6, I haven't noticed much in the way of water in the oil but have ripped it apart to change the intake gasket anyways. The main problem I noticed was loss of coolant and when the car was warm, loss of power. I drove my car to a neighbouring town and on my way back had no power. Had to hobble it home between 30-40 kph. sorry I am Canadian. Reading online told me that vacuum loss would kill the power and the intake gasket could produce vacuum leaks. Should I check further before I finish the repair eg Head gaskets or should I be ok? I would hate to put it all back together only to have the head gaskets be the fault.