So, to you computer gurus out there -- now what? Should I be looking
for anything other than peaks and trends? Is there any parameter, or
combination of parameters to watch out for? What do you guys do with
your data?

On my IO360, max to min EGTs never have a range of more than 70-80 deg
in cruise, often less. On one flight this summer, I noticed that #4
EGT was running about 100 deg higher than normal. Checked both mags
in flight, sure enough, right mag a little rough. 10 minutes later,
everything was fine. Next flight, everything still fine.

I downloaded data from the last several flights and looked at the
data. Sure enough, every now and then #4 would jump up for a few
minutes, then resume normal operation.

I dropped it off at the shop and asked for a check of the plugs.
Turned out one plug wire wasn't entirely tight. That plug was fouled
from intermittent firing. Cleaned all plugs, all fine.

Without the JPI, I would never have noticed, as mag runup on the
ground was always fine.

So what you're looking for is "what's normal" so that you can spot
"this isn't normal".