I've done a search on this and haven't really sorted the issue. To take it back to the original issue...

The car would often bog down and splutter, coincidentally if the fuel level was below 1/4 tank or when exiting a roundabout past 12 o'clock position, so I thought it was down to perhaps the fuel filter and fuel flow, eventually the EML came on (P0171) and the car became more and more undriveable (like a totally lean misfire under load, hardly moving from traffic lights or uphill ~5mph max). Anyway, having changed the filter the problem hasnt improved - I tried running with the MAF disconnected, which made no difference, even with the upstream HO2S disconnected (which I'd assume would create a richer than required mixture based on a default map which should be a better scenario than running lean) it made no difference.

Anyway, todays findings showed me that the rubber elbow was collapsing under vacuum at the rear of the inlet manifold, so I fixed that, cleared the fault codes and went for a small test run around the block. It is slightly better but still runs what I would describe as excessively lean, occasionally hesitating under load and with any more than 1/2 throttle.

I can hear the fuel pump working but I'm also aware that they can be a problem - based on the original symptoms is it possible that it could be failing? I can't get any fault codes to reappear (not even pending codes) and I dont want to risk taking the car too far on a run for fear of it not returning/causing damage.

I've tried a search, as previously mentioned, and I can't seem to come up with any other possibilities ? No visible vacuum leaks, new ngk iridium plugs, new HO2S on the way regardless but I don't see it being the problem.