Nissan Altima: 1995 altima loss of power and poor gas consumption

I recently had the head gasket on my 1995 Altima changed. Since then the
car runs very sluggish and I am getting less millage on a gallon of gas.
The car takes forever to accelerate and seems to rev high for a very long
time before the transmission kicks in and changes gears. I had the Mass
air flow sensor cleaned and the air sensors changed didn't help much. Any
ideas on what the problem may be.

dude, anyone can replace it. it would take 25 minutes ,and an old lady
could do (sorry im not trying to be sexist)it. it would only cost you the
gasket (part price). im sure you already have the tools. you just need a
tool to remove those securring nuts. i think they are 10 mm... you a 10
mm socket, and you remove valve cover... take off old gasket, put new one
on, put it back on , screw them back on.. done. i mean, i would hate to
have u charged 200 dollars to something so easy to do your self. it's
easier than changing the oil!