I only use V power in mine. Around 18 months ago I started using tesco 99 and within a couple of tanks I was getting pretty bad misfires. Switched to v-power and it continued until I changed the coil packs.
Fast forward another 12 months and I put a couple of tanks of tesco 99 through it and it started misfiring again. Back on v power and it was better but needed new spark plugs to completely sort it.
Scared to touch it now, probably coincidence but a problem always seems to pop up after a few miles on tesco 99??
A tank lasts me 6 weeks these days so a few pence a litre makes little difference so I'll just stick to v power