Is there any trick to removing the fuel injector plug clips on a 2001 LS 430?

No trick. Just pinch the connector from the top and bottom and wiggle. It takes a fair amount of force from the top to release the lock. Do not pull by the wires as they can easily be pulled from the connector. After doing all 8 of mine my fingers were sore for a few days.

I found that using a small needle-nose type vice-grip worked well to pinch the connectors latch...