Thanks ktm, think I'll pull mine down and sort it properly, once and for all. The ball still whacks the rivets on the way past the diverter, so thats got to slow it down a fraction. I just did a test on it before, and time is now in the mid 90 - 100 mark, so definitely an improvement. Goal is to get it down under 10, so the ball is just a blur... :)
I also put a couple of drops of WD40 on the multiball hold/release shaft until, the new parts arrive. Fixed the problem straight away, but I'll do the replacement when the parts arrive. Now it even releases at timed intervals when the game ends if there are any balls left in the chute.