Vehicle won't go over 55 with new transmission.

My wife has a 95 Ford probe. Have had it for 8 months and have already spent $4,200 on it. Has a new tranny with 3 year warranty and have put 3 throttle sensors on it. It appears that the sensors have been the issue so far, but I believe they have disguised the newest problem. While making a routine 40 mile road trip the other day, the vehicle began being very stubborn. By stubborn I mean it refuses to go over 65, then after fur thing driving, it refuses to go over 55. At one point it got so bad as to slow down to 30 going uphill. When in low gears the car kicks ass! But after second it's not worth a darn. I strongly believe I may be facing a fuel pump issue, but would like professional confirmation. If you could provide any guidance I would greatly appreciate it.