fuel pressure

Mine slowly drops from 43is slowly over time, I'd say a number of hours.

The FPR on the 2nd gen seemed up to the task at regging the higher flow of the 255. Was about 42 psi (38 psi is standard according to bgb but I've not seen one stock that runs lower than 40) on the stock pump and stayed roughly the same on the 255. Primes a hell of a lot faster though - I used to sometimes have to crank it a bit before there was enough fuel pressure to get it going but now its instant.
 
Generally mine would have a small amount of residual pressure the next morning if id driven it the evening before.
 
If you're losing pressure check injector seals on the rail and the regulator (procedure in the bgb). In an old camry I had (3sfe I think) it buggered up and ended up using a different reg on it.