ECU is a sealed unit that has no servicable or tamperable parts in it.
If the ECU is in question, then I'd consider checking the harness first. (much higher probability that the harness has a problem than the ECU going bad, and for the most part when they do, you have nothing let alone a lack of power)
I was up in the air about the fuel pressure gauge too, until I stumbled across
this at Autometer. (these are available in silver face w/red needle and black face w/red needle. Housings and bezels for all are chrome. Click the 1 1/2"(38mm) link to the immediate left of the picture to see the other faces. Also note that you'll have to get the P# for the one you want and carry it to the shop/parts store/wherever, as Autometer doesn't sell directly from thier site)
That, (around $40 IIRC), a bit of SS braided brake line, (about $13 for non-DOT 18" w/ends already on it) a T fitting and appropriate line adapters (around $10) all from the local hot rod shop along with a hand made mount and it now resides on my firewall between the washer fluid container and the hood latch in a very nice deliberate looking fixture.
Not saying it's the way everyone should go, but it does kind of reconcile the $ used to purchase a pressure gauge, looks hip, and makes me feel a lot more warm and fuzzy than if it were just sitting on a shelf waiting years for it to get used again. (besides it's kinda fun when people ask WTH it is
)
EDIT:
BTW, where and how I've got that mounted does allow me to actually slip the gauge up out of its mount and lay it on the air cowl with the hood mostly closed so that it can be read while testing out on the road.