Hello, Now more wheels are good (don't ask me how I know )........but we must not forget the ones that are in the queue! Regards, Michael.

Sorry Nick when I said vacuum it was the kind of induction imbalance you mention i was thinking about. Although wasn't sure if that would just arise from throttle balance or from the various joints in tje inlet tract and vacuum connections. 

Those are fine very good points, thanks you. I spent this evening cutting out gaskets and replacing the rubber o ring spacers between manifold and throttle bodies.  It now all bolts up tight so hopefully that'll reduce any vacuum leaks. Next up will be to check the linkage settings (only one link as I have two shafts each containing two butterflies).  Change the fuel filters and try some more driving and troubleshooting.

Could be a vacuum leak. Though this would likely mess up the idle as well. One of the “joys” of ITBs is setting both the static idle (throttle stops) balance, but also getting the linkage to  pick them all up equally and simultaneously. This is also a thing with carbs, but the added wrinkle with injection (as touched on previously) is that while unbalanced carbs will maintain roughly the right AFR as each barrel sorts itself according to airflow, injection won’t. This because (unless you have a really flash system), the load signal (either MAP or TPS) will be an average (ish) of all cylinders and the ECU will dose all cylinders equally based on that. So if the air isn’t equal too, those with more air will be lean, and those with less will be rich. This effect will be most pronounced at small throttle openings and also, if your idle balance is good but linkage pickup is not, you’ll have a decent idle but it’ll still run like crap just off idle. (Guess how I know this ).  If you have 4 pots with paired throttles it should be reasonably simple. 4 individual a bit less so. 6 individual, with both settings separate on each is a bit of a bugger….

Seems very plausible Nick. You have a lot more experience of this injection malarky (notdifficult as mine is effectively zero). However I was thinking about the problem this morning after reading the post and my thought was that is felt like an induction/vacuum type problem too.

I used an Innovate LC1 for many years in the Vitesse. It became a bit cantankerous and got swapped for an AEM, which was very problematic, so it got returned and swapped for a Zietronics one, which seems good.

That’s very cool  And educational….. I’d never heard of rock cannons before, Welsh or otherwise.

This could well be a throttle balance problem. ECU works on the average engine load across all cylinders so if one or two throttle bodies are “picking up” a bit sooner in the throttle travel they’ll be getting more air and thus going lean. Even just one going lean or misfiring at low rpm will make you AFRs look high (even if it’s misfiring due to being rich)

I have used LD performance stuff, seems to work OK though it has used a couple of sensors in 50K.

I saw this, and at first was sceptical, but Welsh Rock Cannon were a real thing!