I used to have a 52-reg 307 2.0 Auto and in two years it had endless engine management/electronics faults. Got to the stage where I almost had my own seat in the local dealer's Reception area. Finally got rid when it went to full throttle, in a 40mph zone, of it's own accord. The Peuheot diagnostics computer said there was no fault, which was extremely worrying.
Think professional look-see is probably your best bet as the multi-plex wiring systems can be very tricky.......every thing ties into everything else.