I own a C5 estate.2.0 hpi exclusive.It was my dads who recently lost his battle with cancer.He only wanted £500.00 for it.It is an 02 .The engine is 148bhp.My dad paid £800.00 for it 18 months ago, and had spent over £600.00 on parts/service.I have receipts for over £2k from previous owners.I recently had to replace the radiator fan, EGr valve, spark plugs, air filter, and had an engine anti pollution error too.I have spent £500.00 my self.I was recommended to use 97 octane fuel, as this would prevent filters clogging, and eliminate the engine anti pollution problem.I have been using high octane for around 2 months now and the car runs smooth.I did have a problem with performance and sluggishness.I put BG44K in the fuel tank, ran it to near empty, then filled up again.It now performs like a racing car.I think that if you use high octane fuel as recommended by Citroen, and put a can of BG44k (around £12-£18 a can on ebay),in your fuel tank, then you shouldn't have any problems.