Valve seals and or guides are usually associated with high oil consumption but no smoke. Head gasket problems produce white smoke which is steam and higher temp guage readings. This condition can be easilly checked by sniffing the coolant for hydrocarbons with an infrared detector. I suspect you may have an injector wigging out causing a cylinder wash or a cam oiler tube coming loose.You may even have a computer going South. I hate intermittents.

Good luck,
Peter

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