Ford Repair: 1995 mustang gt, vacuum leak, mustang gt

Question
i had a few questions 1 is im having a problem with my engine the rpms jump up and down while at a stop and has stalled a few times i have changed the fuel filter, spark plugs and had the timing done. mechanics have told me that i have vacuum leak but im not sure and i have the check engine light on but i had a mechanic try to check it but the obd2 is messed up and wont get a reading from it. so my concern is what do you think would be wrong with the car and is it possible to replace that obd2?
thanks for answering when ever you get a chance

Answer
I am pretty sure your 95 Mustang is not OBDII, unless it is a late build California car. If it is OBDI, the connector might be damaged and not able to connect to a scanner. Not sure if that connector is still available, you will have to check. In the event the connector cannot be replaced, the codes can be retrieved manually. You should be able to find that test procedure on the internet.

Sounds to me like you might have a vacuum leak. This engine was prone to the intake manifold plenum gasket leaking, that is where to start I think. In any case, you need to find out what codes are stored or active.