Mine did it on cold start only. Typically at least 6-8 hours of cool down time, but most often it required entire overnight cool down.
As Mark pointed out, I would do the Oil FIlter Checkvalve first, its a $15 part and is relatively straight forward.
The Oil pump relief valve is a +/- $60 part. While I have been able to remove & clean my old part and reinstall, I have not yet discovered how to install the new update part.
Also, I assumed you were reffering to the the valve train update of Technical bulletin AF05.00-U-1300AG and refers to a part number of 119.180.02.66. In comparing photos and the CD Rom drawings, I noted that this refers to an "oil bridge connector" which appears to be a metallic "bridge cover" part.
As I am not a certified mechanic either and can only refer to the documents I have obtained through the guys here, I would recommend that you confirm this with the parts guys at MBSHOP. They can give you part numbers and provide the parts too. I did notice that Donnie (Benzmac) commented in this thread on this upgrade. I can only surmize that the "bridge connectors" are "oil tubes" and that they have o-rings inside them. The above service bulletin number should be the correct one. I have a printed "faxable" copy if you need it. However, I gather that this applies to more of a lifter type noise and less to a "racka racka" noise.
As for the origin of the word "racka -racka", I am not certain where it began, but unfortunately I suffer endlessly from use of the phrase with my mechanic friends. I called them in pun, to ask "what does it mean when your lawnmower goes "racka-racka" and smoke billows out, when they finally quit laughing (about an hour later) they simply replied its time to get a new lawn mower! "Well, even I knew that!. Now the mower has been modified with a slightly larger engine and different pulley sizes to affect blade rotation speeds. The stock tires do have a traction limitation now even on pavement, but the thought of adding ASR seems a bit overkill. My neighbors tease me about mowing the grass with a stop watch, but its all in good humor.
Sorry for rambling, hope this helps.