I have a 2nd set of delivery valves I cut myself. It runs like a raped ape with them! However it idles like crap! I didnt remove the whole collar on them, just ground 2 opposing notches in each one. It required the idle to be lowered when there in. As to why it idles poorly? I know i need new injector nozzles and my compression isnt the greatest but theres more to it that that. It might be some kind of pressure wave deal? I wish i had more time to play with them, try diff pop pressures, timing and stuff.