Ported JHM head noise--valve guides too short?

[Andrew J]

I had my engine rebuilt as the strongest NA I could reasonably build in 2018. I installed pretty much anything I could get from JHM. (It was that or buy a new car. This was before the RS6 invaded.) Car runs really strong, but I have been having problems with noises coming from top end. Electric cam timing adjuster failed a year ago. Replaced that. But but the engine still had a knock. At this point I have less than 15k miles since the rebuild. Pulled the motor again, timing chain adjuster failed, and it at least one lifter/follower looks bad. Seems like that the problem is solved. However, my mechanic who has done all the work started pulling the valves just to see if we might have a problem there. Here is the issue he flagged: the valve guides have been cut down as part of the porting process. He is worried that this is allowing the valves to have more play than they should. The measured clearance is 4/1000, he said the limit is 2/1000. He also said that the guides were knurled, which he thought was strange, even suggesting that it was a shortcut for doing the work right and replacing the valve guides. He is suggesting replacing the valve guides and leaving them at the stock length. So my question are:
--Does anyone have experience with JHM modified heads? After I bought the heads it seems like they took them off the market not long after.
--Is shortening the guides cause for concern? Yeah, I know, depends on how much. My guess is 25% to 50%. If that matters I can get the data.
--Will stock guides reduce whatever benefits I got from porting in the first place?

I love the car, want it right, but don't want to lose all the performance I paid for. HELP.

YES, I HAVE TRIED TO GET IN TOUCH WITH JHM, BUT THEY HAVE NOT BEEN RESPONSIVE. EVER! YOU ONLY GET ONE CHANCE TO LOSE A CUSTOMER.

[Andrew J]

I guess it is clear from the thread, but I should mention that the car is a B7 S4.

[DR.Death]

Yes and no. Really mostly no.
A knock could be: a bad lifter, wrist pin slap, a bad chain tensioner, and maybe the guides but that’s usually more of a chatter.
Do you have a video of it running?
The car should have been run with a stethoscope 🩺 to see where the noise was from. Not a screwdriver and not a closed end scope!
The guides being loose by .02 will cause bad seat wear. It has not much to do with the length at lower mileage. Get new valve parts and install them. Long guides can restrict the flow. And for sure should be at least necked down but if your not going for maximum performance then don’t bother cutting them flush.
Knurling is a bandaid not a solution.
They usually leak before they chatter though.