Tyres or power?

[nick61]

I have recently bought a 2.7 fitted with Pirelli P zeros to replace my 2.5 which always wore Michilen pilots. After driving for a number of weeks and the roads being mostly wet, the 2.7 feels a little twitchy and less glued to the road than the old 2.5. Can this be the slight increase in power or would you put it down to the tyres?