Check Engine/MAP sensor problem

Ok well about two month ago the check engine light came on in my 95 GSR when i put my random tech highflow cat on. I figured it was just from the O2 sensor in the cat

i just checked the engine code and it's throwing a 3 and 5, according to the manual for the OBDI ecu it's saying MAP sensor.

How serious is this and what exactly does it mean? Should i not be driving my car?

It runs fine, no lack in power at all.

did you disconnect the negative terminal of the battery before you changed the cat? if not then disconnect it and leave it disconnected for about 15/20 minutes, thsi resets the ecu, start the engine and leave it idling for a few minutes in order for the ecu to detect the changes made to the cat...i dont know why the map sensor is effected though, but if the check light comes back on then check that the map sensor(on top of the intake manifold) is secure, failing that bring it to your local dealership

you said it was throwing 2 codes right? What's the other one? (besides the map sensor)

The two codes 3 & 5 are both map sensor.