The PTS engine's needles will "walk" with the vibration of the engine, throwing off all of the adjustments.

Even though you may have it perfectly tuned, the "walking" of the needles (both high and low) will cause it to misbehave.

Assume that the engine is completely out of tune and have someone help you with it.

If they do, make sure that they are aware of the limters. To move beyond the limiters they must NOT force the needles, but rather release the retaining cap screw on the limiter itself, adjust then retighten.

Take the opportunity to remove the high speed needle altogether then bend the ratchet clip so that it applies more pressure, preventing the needle from "walking" in flight.

Tighten the low speed limiter while pushing it in against the engine to produce a bit more resistance.

Once you have the engine tuned, lock the low speed in place using a wire-tie or other mechanism.