What kind of problems could high fuel pressure cause? Crappy gas milage? Anything else?

I checked my fuel pressure and here were the numbers:
Pressurized, engine off = 50psi
Idle, Vaccum line connected = ~47psi
Idle, Vaccum line disconnected = 54psi

I have an adjustable fuel pressure regulator and tried to adjust it, and got it down to about 47psi with the vacuum line disconnected, but then broke it and have no way of adjusting it anymore (the last guy to adjust it over-tightened it). Will the PCM eventually re-adjust to the original pressure?

 

The problem with running high fuel pressure is the way the PCM responds. When the PCM sees (via the O2 sensors) the extra fuel flow caused by the higher than stock fuel pressure, it starts to reduce the long term fuel corrections (BLM's), to lean out the mixture. So, in closed loop, your BLM's will cut the 11.4% extra fuel flow that your injectors are flowing ar 54psi. That assumes that is wasn't already cutting fuel for some other reason, because the total available cut with the BLM's is only about 15%.

Then, when you go into power enrichment mode (PE, aka "WOT") since the BLM's were cutting fuel in closed loop, the PCM will default to 128 BLM's and you will end up running rich because of the 11.4% excess fuel.

All this assumes that the PCM has not been "tuned" with an injector flow constant consistant with the 54psi fuel pressure.

Bottom line.... may not hurt you in closed loop, but its going to run very rich at WOT.

What brand was the AFPR? Why not just throw a stocker back in it?

 

Thanks for the reply. I don't have the stocker, I bought the car with this on it. To be honest I'm not even sure what brand it is, but it looks very much like the Holley one I've seen.

Looking at a few logs only makes it more confusing. With my old O2 sensors I took an average of their readings in closed loop, and got about 490-500mv. With my new ones (put in about 2-3 weeks ago) the average was right on the money, 450mv. The BLMs averaged around 123-124 before the new sensors, and are still in the same general area now. 123 for the left and 126 for the right. I think they would be lower than that. Gas mileage was about 13.5mpg before the new sensors, then right after went up to 15, then suddenly down to about 12 where it's been ever since.

My PCM was tuned by Brian at PCMForless, excellent job he did. I didn't specify changing anything with the injector flow constant, and I don't think that's something he'd do normally.

The car has signs of being rich and I never could get it right. Between the bad gas milage, the backfiring at higher RPMs, and the fact that you can smell it almost before you can see it . I was hoping I finally found the problem...

If you want to check out the logs heres two of them. The first one I did about a week after putting in an LT4KM, but before the new O2 sensors. The second I took about a week after changing the sensors.

After LT4KM

After O2 Sensors

Thanks for your help!