Hi. Sorry for the late response.

Yes, four lambda's. All giving a high output of 0.8-0.95 when tick over is struggling at 500 revs. Engaging the gearbox doesn't drop the revs further but while driving there's a flat spot when pulling away.

However, when full operating temperature is reached the tick over is steady at 650 (was once 750) and engaging the gearbox drops the revs to 550. The drop is to be expected, just needs to be a bit higher. However, when driving and stopping at junctions/roundabouts etc the tick over is initially struggling at 500 revs but after 10-15 seconds recovers to 650 and pulls away as quickly and fast as you'd want. But pull away before and there's a flat spot. Stationary post Catalyst lambda's at this point are 0.5-0.6. Pre-catalyst sensors flip regularly regardless.

At 4000 revs post Catalyst sensors drop to 0.02-0.05 which if I'm correct shows the Catalysts are doing their job.

Cold start is 1050 revs but as the temperature gauge rises this drops to 500 and when the ecu shows a temperature of 80 the tick over slowly rises to 650 as mentioned above.

It's like there's something only working when full operating temperature is reached but even then it's not instant.

Operating the electrics like headlights or windows drops the revs alot. But when switching off the revs go higher to 800 and immediately drop and settle at 650.

When I brought the car I was told the tick over had been adjusted lower to save fuel in traffic. Which seemed plausible but it's all electronic and there's no obvious adjustment means.

When you say butterfly assembly, is that the swirl plates I've literally just read about elsewhere?

Cheers.

Dave