1989 Buick Century hesitation and/or loss of power

Car ran great then suddenly it has decided to lose power when you mash on the accelerator to take off, pass, merge onto highway, etc. Changed fuel filter, had new exhaust put on and catalitic converter checked out fine. We are told either TPS, or Mass Air Flow sensor is possible. Both are $300 repairs. How do you tell the difference between the two to help determine which one to replace? Or has anyone else had this problem and could give us insight as to another possible cause?