Quoted from A_J_B:Looking for just a little bit of feedback from some of the veteran pin folk here, see comments below:
2: For trouble with the ramp shots, yes, clean and wax the playfield. It makes a lot of difference particularly on the Captain Marvel ramp. My make rate went from like 50% to like 80% after just a quick wipe-down with Novus 1. This ramp is incredibly sensitive to having a clean and slick playfield. (My hypothesis is that the ball needs to be sliding, not rolling, when it reaches the ramp entrance; rolling makes for just enough friction to sap just enough power for the ball to not make it.)
I put a lexan barrier on the side of my Marvel ramp, but it doesn't really seem to make much of any difference. A shot that's off-axis enough to hit the barrier isn't going to make it anyway.
For Widow and Gauntlet, I found the most important thing was make sure the slope is at 6.5 and not higher. But just by their nature, these ramps will have a lot of rejects - the ball comes in at quite a range of angles and speeds, and the ramps are hard metal that the ball will clunk off hard, not plastic that has a bit of give. I have occasional problems with the ball jumping too high on the Widow ramp so it hits its roof instead of making the shot; I haven't figured out how to solve this.
Mine saw the shavings indicating a bad coil stop after about 250 games. I took it out and yes the brass center piece was slightly loose. I replaced it with Pinball Life parts. Only the left side was bad for me, but if it was then the right side would probably also go soon so I did that too.
3: I installed flipper coil fans and they do seem to help. The Marvel ramp in particular got a lot worse after 20-40 minutes without the fans.