Molly Grease will do nothing to prevent your HPFP from seizing. Poor quality HPFP sieze for many different reasons such as design, manufacturing defects, contamination, broken or leaking seals, etc. Often the only way to see this is to install the pump in your vehicle and pray nothing bad happens. Sometimes you have a bad reused seal that leaks fuel over time. You'll never see this happening till you find your oil is diluted with fuel.
Back to molly Grease - since most people clean oil off their cam followers to check for wear before installing a new HPFP, APR suggests coating the follower surface with molly grease for an extra layer of protection upon the first startup. direct cam on cam follower without a layer of oil or grease in between is less than ideal as one could imagine!
If I understand you correctly you are speaking about the Rail Pressure Sensor located on far left hand side of the High pressure fuel rail and not the rail relief valve located on the right side. You are speaking about the actual sensor, correct?
YOU DON'T WANT TO SWAP THIS PART*
* There are several different versions of this part. Some are simply revisions of the current part in your car - you can use those, but others are totally different versions that read completely differently. Installing a miss matched part will give you a boat load of headaches. The ECU will not be calibrated to read this sensor correctly. It will report the wrong rail pressure. It will either report too high or too low. This may cause you to look for other 'issue' while the real issue is simply a mismatched part. I'd highly suggest you not change this part with a mismatched part.
silly me.
