I have the high speeds and they are probably about the same.BUT come to find out, 2 of them were defective...had bad flow rates and were real noisy after about 15 minutes of warmup.Thought it was the preload being off but no. The rest are slightly noticeable, especially with shaft rockers.Nothing like a tap or anything, more like a sewing machine.
What rockers are you using and what pushrod length??
I went with the Comp Cams 1.7 shaft adjustables which adds to the over all noise level.Expensive, but boy are they nice.
I ended up having to shim them 0.030 because they were smack dab in the middle of 2 pushrod lengths after i set my adjustment at 0.050 which ended up at 7.100 then ~0.020 preload. New era told me 7.400 is what i need but it was nowhere near that.