You must first check you oil pressure also, if it has been tapping as bad as you have suggested I would be removing the cam cover to have a look at the followers. They will go in upside down and will soon reck the cam. You should be ok refitting the sump with new gasket but just double check what grade oil that you are using. As for the bore wash to me it sounds like the metering head is dicking around tbh I personally have never had any luck with them. All can say is that if you find some that truly understands them but more importantly is willing to to take it on then I would just pay them what want .

Adder