I did a compression test to diagnose a cylinder misfire problem. Compression was good, if a little high: #1 at 248psi, #2 at 241psi, $3 at 235psi, and #4 with 247psi (average of 3 test results). Tested warm, WOT. Also put in new spark plugs and swapped coil packs around to no avail.

With good compression results, would a leakdown test give any useful information?

 

Yes, leakdown will show leakage that a compression test cannot.

 

It's at the mechanic now. My solid CEL turned into a blinking CEL. Hope I didn't wreck anything with my shade tree wrenching.

 

That means that it went from a radom mis fire to a major mis fire. See if your mechanic can Check out the fuel injectors.