Misfires and tapping

[clickman]

2001 Boxster, 2.7L, 90,000 miles. Owned since 2006.
Drive about 5000 miles per year. No winter driving.

I put the car to bed for winter in October. Changed oil, added fuel stabilizer, hooked up battery maintainer.

Early May: first start of year, moved vehicle in garage. Had the normal short-term chain rattle on startup, but then all normal.

Mid May: disconnected battery to replace headlight/wiper/turnsignal switch behind steering wheel. Started engine afterwards; seemed to run rough but attributed this to needing to relearn. No CEL.

May 30 (yesterday): At startup notice tapping from engine. Then noticed solid CEL. Ran engine for about a minute while moving car in garage. Shut down and dumped codes:

P0300 Random/multiple cylinder misfire detected
P0301 Cylinder 1 - misfire detected
P0303 (pd) Cylinder 3 - misfire detected

IMS Guardian not alarming (metal in oil pan).
Spark plugs last changed 2014 (15k miles ago). Replaced tubes same time.
AOS replaced 2014 (15k miles ago).
MAF sensor replaced 2017 (8k miles ago).
Replace fuel filter 2011 (33k miles ago).

Cam deviation (with Durametric and engine hot):
Date Bank 1 Bank 2
April 2015 7.3 2.8
July 2017 6.67 2.50

Research shows it could be as simple as bad gas to as catastrophic as IMS.

I have a Durametric but concerned about running the car any more.

Advice?