During my time in the dealer I replaced several 208 heater boxes for noise from the center vents. I appears the vent seals come off and whistle.
112 and 113's use the same air mass sensor and will start reading lean across the board, in some cases just effecting the idle, in others, affest acceleration and overall power. Does your car have a slight surge on accel? This is a sign of the a/f mter going away.
I'm not sure about the UK's engine management system but, the US specs will do the following:
1) kill air flow meters (mass air flow)
2) stick egr valves
3) seperate front dampers
4) stick fuel pressure regulator (made into the filter here)
5) 202's and 208's have had fuel pump relay problems.
6) of course, the infamos oil control rings coking from the FSS and Dino oil combination.
7) front O2 sensors, both bad and connectors full of water, which can short ME out.
Of course this isn't across the board nor do every one of these do this. I'd be sure to look at the air mass readings, 16 to 21 hg at idle and if it wont make it over 350 when opening the throttle fully, replace it. On the US car you can moniter misfire but, you might not see a thing. It's been my experince that havin a replacement air flow meter around to "try" always helps, if the overall fuel trim is heading for rich limit, swap the a/f and drive it, if it starts moving towards center, there you go.
Project Smoker, '87 603 powered wagon
Hauler, 96 CTD can you say torque?
Toy 73 Cougar xr7 convertible
Acme Automotive Inc.