Nissan Repair: Follow up to my rough running question..., intake manifold gasket, vacuum meter

Question
we decided to try the fuel injector, which I get on Monday from Rockauto.com. (GREAT PRICE) Out curiosity, went and had the code run at Advance Auto. Got a P0300. Random Misfire. I may have jumped to conclusion about it assuming that the cylinder 4 injector was not working. I checked some other boards and found a guy with the identical problem. He replaced his intake manifold gasket and it corrected the problem. His altima had 78k miles. Mine has 150K. Should I go ahead and replace the injector or do you think there is credibility in the other scenario? Thanks again.  

Answer
Daniel,

You could have a leaky intake manifold and you could check this with a vacuum meter.  You need to see if there is an actual leak of air entering the intake that is unmetered.  If too much air is getting in the fuel injection will not meter properly and, as such, there will be a misfire.  If you ohm check the injectors and they are fine and the fuel pressure holds you could look at the intake.  Get a Haynes Manual for the specifics for your car and measure the ohms on the injectors and if any are more than a couple of ohms off replace them.