Its all about balance....
in basic engineering terms a gain in one area will result in an effect or compromise elsewhere. I am convinced that your problem is a clutch /power mismatch. you are only on a stage one clutch and your engine is at least stage 2 tuned. I have been in it, I know!
as mirlock said go with a more robust clutch arrangement and all will be well!
on a more holistic note although the car is capable of the 270 BHP does that mean you have to do it? maybe at this point a small compromise of 20 HP and some really clever mapping to manage the torque levels are the way to go.
remember mate this is your daily driver too..in this respect you and I have much the same outcome in mind, a fun fast car that is also RELIABLE...I will only be aiming for around 220BHP once the Hybrid and FMIC are on as in my mind that is where reliability will begin to become significantly compromised.
mine has proven to be very reliable managing 600+ miles every week without complaint, returning good economy and some laughs when required, the handling is also really nice, not quite as refined as yours but not too far off...currently on about 195BHP and leaves 90% of challengers with a surprised look on their countenances as I disappear of into the distance..not the scoobies and the faster beemers but hell, we knew this when we bought the cars. I prefer that I drive something a little different and in my mind more beautiful than any Beemer,Audi and most Mercs...and definitely prettier than any car made by VW..!
bear in mind our cars are lighter than the equivalent AUDI ,BMW or Merc so 250 BHP puts it up there with all of the usual contenders, added to which it doesn't have dim witted handling, dull interiors and it doesn't feel like a taxi to drive.
no point in comparing it with the Msport versions or S or R Audi's because it isn't one. they are far more expensive to buy and cost more to run than an Alfa GT. my mates RS6 recently required a rad...£1500...and that was from a well priced indie.
also its NOT a sports car ,its a GT, for me it fulfills all of the requirements of a good GT car. comfort,space,power,economy (not usually a feature in a GT car but a welcome addition) and when required a turn of speed.
if I had the garage space to own more than one car at home ,then I would take my Fiat Coupe, tune the beejeezus out of it and have the GT in current state of tune and the Fiat for sh*ts and giggles.
as it is I don't so I need (want
) one car to be all things, so to bring it back around to where the posy started, its about balance.
you CAN push on. clutch needs doing so what the hell do it and then ave a custom map.
I would personally leave it at around 250BHP mark...and enjoy a long trouble free relationship with your Clover, any more and its getting on for twice what the engine was designed to handle.
good luck mate