I recently put a new motor in my mustang. It is out of an 03 mercury grand marquis. About a week after I got the car running I noticed a light tap or tick which sounded like a lifter tap on the passenger side. I got the car tuned and decided I would fix that problem later. Now I haven't drove the car but once down the road and everything worked fine. The other day I go out to my car and start it up and give it a rev or two and noticed that when I rev the car up or I step on the gas the oil pressure drops. Now it doesn't go completey to the bottom of the guage but pretty close. I am kind of leaning towards a oil pump and lifter replacement at this point but was looking to get any other insight from anyone else that may have had a similar problem. let me know what you think.