Well, one step forward, two steps back
Engine wasn't running great with a lumpy idle (almost like muscle car sound!). At first I just put it down to the open header being super loud but we started to get timing codes logged on my ODB reader (p0341).
I checked a few easy things like the wiring to the sensors etc but unfortunately after removing the cam cover we found the timing is out, most likely the chain was stretched and we didn't realise (even though we were able to set it right, which I can't quite get my head around)
Moral of the story is, don't re use the existing chain even if you think its ok
New chain, tensioner and guides ordered...