Just make sure you only do one thing at a time otherwise it can confuse matters.
And make a log of any changes you do for future reference.
Two things, firstly those plug caps don't look standard, in fact I know they are not.Secondly Darrsi is quite right about doing one thing at a time.
If you do four things at once and the bike runs fine you will not know what thing cured the problem, then you will not have learned anything for future reference, do one thing say filter then try the bike for a few miles and see if its made a difference, if not them move on to the next thing, I know it might mean removing the fuel tank for a second time but it only takes a few minutes.
You will learn something and if those same symptoms show there ugly head a couple of years down the line you will be equipped with the knowledge of how to rectify it.
I keep a log of all the work I have done on my Fazer and parts fitted, Dates & Mileage.
Reading through what I have just written sounds anal, but it does give me a full picture of the bikes history since i purchased it and it shows me when things need to be replaced.