Hello all, I've recently bought an S-max 2.5 turbo but thought this would be the better forum to post in as I suspect there are more Focus ST drivers with the same engine on here than S-max drivers!

The car seems to bog down / have a flat spot at low revs and when pulling away from standstill but revs cleanly on WOT beyond about 3k RPM.

It keeps throwing this same P2187 code and a CEL every couple of days which can be cleared with a code reader but that does nothing to affect how the car drives and within a day or two the CEL and the fault code come back. P2187 fault code on my cheapo scanner is described as System Too Lean at Idle, Bank 1. I also scanned it with a proper Forscan tool but it came up with much the same info and no real suggestions as to the cause.

I tried cleaning the MAF which made no difference, and tried swapping it for a pattern replacement which made the problem much worse and made the car almost undriveable (guessing that the cheap MAF was giving inaccurate figures which were exacerbating the problem that exists elsewhere).

Any ideas what could cause this? The car seems to run fine at higher revs or when under full load, but the hesitation is getting on my wick when driving it in traffic etc. Sadly we can't go everywhere at full chat! If it could be an air leak somewhere, any suggestions on the most likely places to check? Car is standard apart from a stainless exhaust fitted by a previous owner so I don't have a boost gauge to see what level of boost it's running.

Thanks!