I've logged over 72,000 miles on my S14 SR20DE drivetrain since 2003. ~6,000 miles were without driven without a speedometer/odometer (while we figured out how to run the VSS)


Maintenance:
I've done nothing but check/change the oil. Might even call it "deferred" maintenance

Performance:
Still has similar power output almost a decade later. Here is a timeslip from last year at Fun Drags at Sears point (now called Sonoma Raceway):

One of my better runs as I was stuck at 14.6/7 @97mph for along time. I know, it's not V6 Camry fast, but it's consistent!
MPG:
Fuel Economy:
Don't hate, I am a nerd and I do keep Excel spreadsheets for all of my cars

Here is a snapshot of when I was commuting and driving alot:

Best: 40.33
Worst: 25.74
AVG: 33.8
open track-day: 17.2 mpg (Laguna Seca)
How about your engine swap, any reports?