As the title says my 92 Chevy Caprice is accelerating realling slowly, and I mean slower than molases being poured out of a jar. It is like my car has lost all power and is running really rough. It does not matter if I floor it or tap the gas lightly the car just will not get up and go for nothing. It takes me about 20 secs to get to 15-20mph. At first I thought my car would not go over forty but it can make it to fifty-five if I have enough road, but it is really hard for me to hold it and sixty is out of the question. The problem did not start until I had a mechanic put a new fuel pump in my car because mine had fail about a month ago and the car has been sitting in my yard for about a month, but it ran fine before the fuel pump gave out. The mechanic told me if I got a tune up and fixed the exhaust leak I have then it should go back to running fine, but I know i had that same exhaust leak before my original fuel pump went out and it ran ok. Oh by the way my Caprice has the 305 v8 motor wit dual flowmasters on it and I changed the fuel filter before my fuel pump quit on me. I was plannin on changing the spark plugs and wires on my car but I have been ill for the last couple of days so it may have to wait for about another week or so. So what do you guys think my problem may be?