just changed my spark plugs using this DIY on Thursday night after racking up 89K miles on my stock plugs. Stock plugs were pretty much fried, causing a misfire on cylinders 1 and 4.
Once replacing my old plugs with new Bosch OE plugs, i had new CEL codes on my E90 in addition to the shakes and misfire when idling. It's now Monday and the car seems to be idling better. CEL went away this morning (monday) as well.
Thanks for the DIY!