I have a 91 F150. 300 I6 with low compression in cylinder 2. Wet/dry test indicates ring problem. I've read some posts on here indicating that a wet/dry test might not hold much merit and that a leak down is the preferred method. Thoughts on this? I put 25ccs of ATF in the cylinder for the wet test. If it is the rings, I'll rebuild it. If it's a valve I'll just pull the head. What are some "tasteful" modifications that could buy me some more power without having to change a whole lot of other things on the truck to keep up. I'm thinking of a cam and maybe some head work so it'll breathe better. This is a SD motor, how does that go with tuning? (A shop, not me) Worth noting : I recently replaced the fuel injectors and front fuel pump /tank. I was suspecting that it had been running lean with a bad injector and burnt a valve.

 

A leak down will tell you right where the issue is and I dont see the need for the gauge to know the % leak down.
Put the hole you are going to check at TDC, valves closed and put a little air in the spark plug hole.
Air out the tail pipe bad exh valve.
Air out the air intake bad intake valve.
Air out the oil fill cap bad rings.
Dave ----

 

I've got the equipment to do that. I'll get to it eventually.