Originally Posted by Alternative
I love how this is some kind of closely guarded secret...
Sticky throttle is common... I think due to the next point
Movement in the throttle plate when partially open (ie sideways movement in the bearings)
Throttle return spring is too weak (ie return force) and the locating tag can break off
Idle adjustment screw doesn't offer enough idle adjustment so you have to use the throttle stop. (which also changes TPS)
Throttle stop bolt can come loose unless you loctite it or put on a better locking nut, or do it up very tight.
On the non Miata throttle bodies:
TPS locating tab is held on by the tiniest of screws. High reving motors can vibrate it loose.
Not all the above issues effect every throttle body. Some are fine and have no issues out of the box, but all the above are fairly common if you search. There is a good reason the Skunk2 products are referred too as Junk2 on the Honda forums. The Miata specific Skunk2 throttle body is actually one of their better throttle bodies...