I've been having trouble with my 99GT lately and I was wondering if anyone had any ideas what the problem could be. Basically when the car starts it runs a little "puttery" at first. Then when driving the acceleration doesn't seem quite right. It seems like the car doesn't accelerate as strongly as it used to. Finally, when I get up to around 45-50MPH the car just completely loses power and the RPMS fall drastically even though I'm still giving it gas. It's rather unnerving and I cannot get over 50MPH due to this trouble. Some background on the car, it is a 99 mustang GT, just under 90K miles. Thing is, I went away to college for 5 years and my dad drove the car for the first three years and then it just sat for a couple of years not being driven at all. Needless to say, the battery was dead and the fuel pump needed replaced. We got both of those things repaired and now I'm having these problems I have previously detailed. Any ideas as to what the problem could be? Thanks so much!