Hi, my main concerns are 1. I don't want to put undue stresses on the engine beyond its safety parameters, or premature failure of parts. 2. I don't want to compromise handling for xtra power, as I presume the car is set up for 270bhp. + Surely Peugeot Sport have tweaked it to optimal performance already.
It starts with the question what your reason for engine tuning is. Do you want improve straight line acceleration? Or more power in the low or high rev range? What is more important to you, just the sheer power possible with an engine like that or to keep that balance of power/torque/traction while driving?
The only mod I did to my R was to remove the top speed limiter. It was something which was really annoying to me when above 240 kmh the fuel pressure was taken away and the car slowed down the acceleration towards top speed. I wanted the R to run free. So it did. There were not a lot of occasions to do +155MPH. But it could do it when asked.
But for the rest, like handling, braking, stability in corners on/off accelerator, LSD traction, I was very happy with the setup. Wouldn't have changed anything.