advice needed

[branny]

i have the mazda 6 tamura, i have fitted a kn panel fillter and i am useing V Power raceing fuel (100 octane), after useing about 3 tanks full of the fuel my car has started to feel sluggish, is it the fuel or the fillter making this happen?

 

[HDi fun]

Possibly neither. It's quite possibly psychological. You've achieved results with a decent air filter and using High RON petrol. To make best use of it you might need to get the ECU control data tweaked to allow more ignition advance under load. Now you've got used to the beneficial effects you feel your car is slightly sluggish.

Even slightly warmer weather can impact upon performance negatively.

I tend to notice such minor changes in driving and performance as well. Some of us are just more sensitive drivers than others. We're the more demanding ones, sadly and are often left unsatisifed when other, less sensitive (and probably more content) drivers are quite happy with the status quo.