1996 Infiniti I30 engine stalling

Engine Performance problem
1996 Infiniti I30

We have a 96 I30T Infinity. It has been a wonderful car with no problems until recently.
Car stalls when you come to a complete stop or turn a corner. Starts right up with no problems.
Inconsistently runs rough when you give it gas then suddenly surges forward and then seems fine.
No Engine light. Dealer can't find problem. They tell me they are not getting a "hard" reading and have replaced knock sensor and O2 sensor, cleaned fuel injection system to try and remedy problem.
Car runs fine for 2 weeks after sensors replaced then problems start all over again.
What else should they be checking? Car has alot of highway miles so not sure if they are trying to sell me a new car instead of fixing the problem?