adding hp to 78 cutlass

Hay fellas,
I have a 78 cutlass w/ a rebuilt chevy 350 4bl holley carb, edelbrock intake, headers w/ dual exhaust. My question is..what else could I do to increase hp...When I bought the car I know it has been sitting for several months..and it seems to be sluggish a little bit..I was under the impression that the carb maybe robibng me of some hp...plus the car was originally frm Mich..and I drove here to Co. and since the air is thinner here..I have noticed that when I start it in the morn..it seems like the carb is not gettign enough fuel?? so I am thinking maybe the carb needs to be cleaned?? any suggestions will be helpful
thanks

advance the timing 2 degrees turn the fuel to 1 3/4 turns on the jets and a double roller timing chain and gears is always a good idea for directing your power and pickup on a v8