i have a 93 hatch obd1 and i put a 96 ls obd2 into it and now i have 2 map sensors, the civic one is right next to the fuel filter. then ls one is on the intake manifold, then there is vacum line from the canister which sensor should get the line and how is this going to work?

 

The ls one doesn't need a line run to it, it reads directly from the intake manifold. Just remove the stock one (if you're sure it actually is a map sensor...) and plug the harness into the LS sensor. It is a round 3-wire plug right?

 

so i should not use the one on the fire wall, but take the plug out of it and plug it into the ls sensor on the manifold?

 

Yes. Technically, the LS one is attached right onto the throttle body, it uses the same type of 3-wire connector that the TPS does so don't get those mixed up...
No need to hook up the firewall sensor to anything...no vacuum source, no electrical...