have a tech2 on my scoob and i keep seeing this 2.5 business can anyon tell me what this is

i know what a tech 3 is i think

the thing is since i had the tech2 done i have had a cold air kit fitted and a turbo to maf housing pipe fitted and i am sure the car is running a little leaner as not so many pops and bangs due to more air getting into it and it definatly feels quicker

also the knock link lights up 1 green on full boost for a few seconds in top gear which i know is safe but it didn`t do before



as you can imagine i want the car to be safe so can this tech 2.5 help