I am trouble shooting a 2002 Mazda Tribute. So far over the last 3 months I have replaced leaking power steering pump, alternator, two of the six coil packs, battery and now it's not shifting right?

So my tribute has had some issues
lately, I need help to figure out what
is going on. I changed the oil and all
spark plugs when I changed the two
bad coil packs. The truck seems to
be shifting fine unless you are over
2nd gear. I don't have any dash lights
on or any other issues. Trick is not
shifting until I let off the gas. What
could it be. I think I know but I am
hoping for the best.