i recently just changed my head gasket on my 90 hatch. now when i let it run for a while (4-5 mins) the gas drops from 1/2 tank to 1/4 tank? how does this happen? and then when i rev it up a little my car doesnt react like normal cars do when i step on the gas it takes a sec? then after it revs it shakes and almost dies on me. what is causing this to happen? is it because my timing is off?

 

check your timing again

 

someone told me its my spark plugs?