verified both the front and rear butterfly shafts and cable aren't sticking on new carb. but sometimes when you rap the throttle the idle stays high, then you kick it once or twice it returns to normal. don't see anything holding it open. thoughts??

I have had the secondary throttle shaft spring not be strong enough to close the secondaries from a part throttle "rap"
I installed a small return spring to the secondaries to eliminate the problem.

I had the same issue with a 4500 that was just barely sticking.

squirter cams can be dry and cause some issues

I have the same thing happening on a new apd. I can't tell why it stays open. My rear blades are barely staying open.

I've noticed my Primary butterfly won't return all the way back to idle and do this sometimes. I haven't really looked into what it could be, but likely just needs a little lube on the mechanism is my guess.

Check your throttle from pedal to carb. Make sure it is clean and not binding any where. On my stuff I like several return springs and I like it fairly stiff. But you do not want all of those springs on the carb or it will wear out and bind the shafts. If your cable is on top and spring is on bottom (or Vice-Versa) then both are pulling against the shaft and that is hard on it and will cause problems. If possible you want the return spring and cable mounted inline at same place on carb to reduce the stress on it. Then it will rotate and return easy and shafts will last much longer. A good throttle and return spring design is important and I see a lot f them of poor design and some are rather expensive big name junk.

new apd here also. ive pressed on anything and everything when is racing. nothing feels likes it off its resting spot. weird. just kick it once or twice fine. two springs at the pedal, and a moroso bracket at the carb linkage with two light springs.

Working in some WD40 to the throttle shaft has solved that on multiple carbs I've worked on. Usually the secondary is not closing completely.