1994 Ford Thunderbird Engine stumbling on exceleration from

I have a1994 Thunderbird 4.6V8 with an intermitent problem that has every mechanic thats looked at the car stumped. This car can run fairly well for months at a time before all hell breaks loose. When it does, I get erratic idling, slugish exeleration, stumbling on moderate inclines, and last, but certainly not least; a steerability problem. The front end is all over the place, and it sounds as if im going to loose the front suspension. I changed the speed sensor since someone mentioned to me that when they fail, the power steering goes into default mode which is power assist for easy parking manuvers, and will stay this way at all speeds. Is this correct? Additionally, the car now consistantly stumbles and wants to stall from a dead stop, and only improves if I get on the pedal a little bit. I have had the front end problem problem over ten years now without a soulution. The stumbling from dead stops is something that started recently. Keep in mind this car was just taken out of storage less then a year ago after sitting garaged for five years without being started. The only thing I replaced was a faulty fuel pump when I put the car back on the road. Any Ideas or advice would be appreciated.