You'd want to do a Leak Down Test
to pin-point where the problem is. You need a LDT tester for that. You can pick them up at Harbor Freight, Northern Tools, and any of your parts houses.
A compression test will tell you whether you have a problem or not, it won't tell you what the problem is. A LDT will tell you very closely where the problem is.
Instead of having to diagnose as you disassemble, this will tell you where the problem is before you do anything more than removing a spark plug and fuel-injector connector.
I like Eric The Car Guy
, he does a good job explaining things. Here's his video on how to do a LDT. It is a little long at 27 minutes.
ETCG has a website with a lot of very good instructional videos. I've done a bit of learning from his videos. Many of them are up on YouTube.
If this stuff helps you guys, please click on the "+" sign in the bottom right of the posts (called Props) so I'll know whether or not I'm being helpful.
Hope that helps. Merry Christmas!