P0172 & P0300 codes intermittent

Hey guys, so I've been having a P0300 code intermittently and recently started throwing a P0172 code in my 97 3.0 ranger.

The P0300 code has happened about 3 times that I can remember, the truck would suddenly start misfiring hard for 30 seconds then smooth back out and be fine and the code would go away soon after. The P0172 code showed up recently in the past few weeks and won't go away. I read in the explanation of the P0172 code somewhere that sometimes you will also throw a P0300 code and that they could be related which is why I'm mentioning them together. (Although I haven't had them at the same time yet)

So, I want to give a short backstory on my truck to help figure out the issue. I've had the truck since 107k miles (currently at 123k) and have done a bit of work to the truck. So in theory (although sometimes parts fail prematurely or just are bad out of the box) I can eliminate some of the potential problems.

The P0172 code is typically caused by these things according to my research:
-A dirty MAF sensor
-Bad O2 sensor
-Leaking fuel injector
-Faulty fuel pressure regulator
-Vacuum leak
-Bad coolant temp sensor
-Worn spark plugs

So, some of those things I have already replaced: maf sensor and air filter, remanufactured injectors, fuel pressure regulator, plugs & wires. Which leaves: bad O2 sensor, vacuum leak, or bad coolant temp sensor.

Onto the P0300 code (because it could or could not be related to the P0172 code) the causes seem to be:
-Low fuel pressure
-Vacuum leak
-EGR system malfunction
-Faulty coils, plugs or wires
-Camshaft or crankshaft position sensors
-Bad ECU

And again some of these things I have already replaced: I fixed my low fuel pressure issue when I got the truck I believe (had a hard time starting due to low fuel pressure), the EGR system seems work correctly because I threw a code for it before due to a leak that I fixed, I've replaced the coils, plugs and wires, and I've done the camshaft and crankshaft position sensors. So that leaves: Vacuum leak, or a bad ECU.

So, what's interesting to me is that between the two of those codes a vacuum leak could be a common cause. Otherwise I'm potentially looking at a bad O2 sensor, a bad coolant temp sensor, or a bad ECU - assuming I can rule out anything I've already replaced.

I do think my truck has a vacuum leak or intake leak because it makes a faint whistling noise when it runs, idles a little rough, and has major rev hang between shifts. I can't find a vacuum leak though, all the lines seem okay so I think it's an intake leak that is hard to spot. However it's odd to me that it's pretty rare that I throw the P0300 code and it'll go away soon after and only recently started throwing the P0172 code. If I've had a vacuum leak this whole time that doesn't make a whole lot of sense in my mind.

Anyway, I'm wondering if anyone has any insights to these issues? I know this is a lot of information to throw out there but I thought it might be helpful in determining the problem. I don't just want to throw parts at this truck hoping I can fix it eventually.

New O2 sensor did away with my 172 code,

I found the source of my problem and fixed it! It was due to a leak in the lower intake manifold gasket. I replaced the intake manifold gaskets and no longer have the p0172 code. I haven't thrown the p0300 code in a long time but it'll be interesting to see if that never happens again either!

For anyone with this check engine code (p0172), I'd highly recommend watching this video. - https://www.youtube.com/watch?v=qJWnpiCj-6A - if you have a diagnostic scan tool (I have a cheapo chinese one off ebay and I was able to do most of these tests) it's pretty quick to figure out the issue using his tests and some patience.

I hope this helps someone else!