Coolant System Question

2001 F150 V-6 4.2L 2WD

I noticed a small amount of what appeared to be antifreeze where my truck was parked in the garage and figured it must have come from a joint in the exhaust system upstream of the cat converter. I did a pressure test of the cooling system with these results: The gauge dropped a very small amount during the test. That drop could be in the test equipment or the system. I then left the test equipment installed, pumped it up to 16psi and started the engine and let it reach operating temp. The pressure did not increase nor did the gauge fluctuate. According to the instructions with the test equipment, the pressure would increase if the head gaskets were bad and the gauge would fluctuate if it were a compression or combustion leak. And yes the coolant level was low, but it is NINE years old and has never had any added. Ok, I know it should be changed. NO THE TRUCK DOES NOT RUN HOT. And no white smoke from the exhaust. I don’t see any leaks except what I mentioned above. Connected my Scan Buddy tool and it showed NO codes.
Would appreciate any suggestions.

I don't see that there's anything wrong with it. Just watch the coolant level and your garage floor. Did you notice any more coolant leaking underneath your truck when you did the pressure test? If not, I wouldn't worry about it much. I don't think liquid coolant would come out of an exhaust as the temp in the combustion chamber would turn it to steam. Have any other vehicles parked where you usually park your truck? You've done all the right things.