The irony is it was me who broke the tabs on the original sensor (I think) because I swapped the air box and concertina hoses across from the old silver V6 before it went, as there was a small tear in the large concertina hose from the air box to the throttle plate, and the screws in the air box were all rusted too. Yeah, I'm picky, but when the old car was supposed to be getting scrapped for parts, (not resold on ebay *cough*) naturally I'm going to swap any easily swappable stuff that is in better condition
I wasn't sure about keeping the air temp sensor from the silver car (whose tabs were also broken) in the air box but in the process of swapping the sensors between the two air boxes I broke the tab on this one too! 
Now that I've fitted this new one I can see why - the hole that they go into is keyed with 4 small slots so that you push the sensor into the hole when it's on about a 45 degree diagonal with the tabs lining up with the slots, then turn it 45 degrees to lock it into place - the strange thing is I've only ever seen them sitting at this 45 degree angle on both V6's I've had, and when you turn it around straight (in line with the filter housing) to lock in place it then pulls the cable fairly tight, almost as if it was not designed to be turned to that position, yet if I left it at the 45 degree position that I inserted it at (and which the original was sitting) it was trying to fall out on its own...
I would certainly check the air temp sensor on your V6 conversion and replace it if there is any doubt - OE parts are available on amazon (of all places) for about £6.25 so it's a bit of a no brainer.
I'm not surprised that reading too high could affect performance - remember on the Silver V6 at one point when I thought it was running too lean I connected that variable resistor in series with the air temp sensor to fool the ECU into thinking it was colder than it really was, thus making the mixture richer - reducing the apparent temperature reading by about 10-15 degrees was enough to make the mixture about 10% richer.
Before replacing this sensor I have occasionally seen on the Lexia air temp sensor readings in sunny (~20 degree) weather as high as 40-45 degrees after the engine bay has 30-60 minutes of heat soak from hard driving, and whilst the intake air will be warmed quite a bit by the hot air box that always seemed unusually high to me - if the real reading should have been say 35 degrees instead of 45 degrees in those conditions then that could easily cause the mixture to be significantly too lean, and a lean mixture on a hot hard worked engine will make it more prone to knocking and needing the timing cutting back by the ECU...
I haven't checked the air temp reading after a hard drive since, but as the weather is getting colder now I probably wouldn't be able to reproduce those conditions until next summer anyway.
It feels like a caged animal that is pulling at the leash and just rearing to go. It is honestly that zippy and punchy today that I'm amazed. I thought it was going quite well yesterday, today it is incredible. 
Or at least get it working again, as the repair uncovered a previous bodge job! 
Even after applying some grease and stretching it as much as possible I was only just able to get it on as far as shown in the picture... I don't know how long it will last or whether it too will split. There seems to be a join in the pipe indicated in the yellow circle - is that joint and the seemingly too small pipe original or has someone replaced it ?
