[FerociousP]

afr swings at cruise are most likely attributed to the ecu falling in and out of closed loop... or not even reaching closed loop... and that could be to a variety of reasons.

Almost none of those reasons would have to do with fuel pressure. Are you running a stock 1-wire O2 for the stock ecu? If not, are you using the simulated 0-1 volt out on your wideband to the O2 input on the ecu? Have you made any adjustments to the cruise area of the map where it is now too lean and causing hesitation? If your ecu even reaching closed loop mode?

I don't think you are looking in the right place to fix your problem. These ecus were designed to work in a stock capacity with stock components... Its very easy to make a change that the ecu cannot compensate for, or even knows about. Yes these are old ecus with old technology, but the technology worked for many years before people started modifying them.