To answer the question regarding access to the valve covers with/without the heat exchangers on... look at the following pictures. The first shows access on the left side through wheel well with heat exchanger on. Looks accessible.
Second pic shows right side looking through wheel well and access is not out of the question but by no means easy unless you move the oil lines perhaps. Last pic shows access via underneath but without the heat exchanger. There is minimal access from the bottom with the heat exchanger installed. I guess it could be enough if you worked in tight spaces at various angles. Not out of the question.
Seems like it's worth it to remove the HE to do a valve adjust atleast on the right side but I could be missing something.
