Spark plugs.

I have been using NGK sparkplugs BPR 6ES. I thought I would dig deep into the sporran and splash out on a set of iridium plugs BR8EIX. Now I know that this kind of extravagance is a bit out of character for a Scotsman, but what a difference they have made to the performance of the bike. It seems to be running a lot better, particularly at low revs. My son tells me that there are a lot of fake NGK’s for sale on e-bay, so it’s possible I have been running with dodgy plugs. That’s why I’m noticing an improvement in performance.
Any thoughts on this?

Maybe you have a rich area and they are doing a better job of burning the fuel.

There are heaps of them around I got caught a while ago when I bought some from ebay. I reported the trader but ebay did nothing.
thecounterfeitreport.com/product/400/Ngk-Spark-Plugs.html

I've been using NGK Iridium's in EVERYTHING for years. Can't find a better plug so far, although with a waste spark system, according to the plug manufacturers, you should be using a double platinum plug. The reason they put the platinum wafer on the ground electrode was to accommodate the wear characteristics of the plugs in the system which fire from the ground electrode to the center electrode. (which in our case, there are 3 of them.)

Yeh I've had the iridium plugs in the 13 for a while now, runs great

I've also been running iridium plugs in my 13 for ages - seems to really help start up and initial running.
Also run them on my Z900 - exactly the same improvement.