Has been a while since my last post.
I wanted to give plenty of time to reasonably evaluate some results & driving a few thousand miles before I posted.
Well I can say I am very pleased with the results.
I have upped the boost a little more, and still:
Fuel economy has been at a steady 28-30 UK MPG, consisting of mainly longer runs on A roads /Motorway runs, including some town driving, and being stuck in slow moving traffic on the M6 for over 1 hour - which is to be expected if you live in the UK.
Engine has been smooth and Quiet
The Turbo spooling sound is noticable, unlike pre groove, where it wasnt noticable at all.
Plenty of low end torque (takes off from 2400 RPM)
Engine oil still clean.
More Power (from increasing boost a notch)
I cant / dont need to put my foot right down, as now the extra torque is causing some slipping of my clutch!
(my 16T will need to wait a little beore going in!)
The engine seems to be running cooler. (I say seems as I think my temp guage has temp compensation board, so its not as straight forward to read from the gauge accurately, but has never been past (or even up to) dead centre, even on the occasions we have had exceptionally hot days for the UK. Pre groove the temp gauge was pretty much dead centre, but difficult to give an accurate indication on this.
Today I decided to index the plugs (a little better by moving them to other chambers) , and at the same time take a look at them visually.
Visually, from the plugs, the engine appears to be running well.
I was a little surprised that the plugs were pretty spotless round the ceramic surround centre electode side facing towards the main groove (or centre of the chamber) with light carbon deposits on the opposite side (near the chamber wall).
Regarding the indexing of the plugs, as you can see from my head groove photo (below), the spark plug on the right was probably in the WORST position regarding indexing terms.
Interestingly, the white surround on the centre electrode was still spotlessly clean on the edge near the main groove, and the coating on this spark plug ground electrode was this light blue colour, talked about.
Furthermore, the exhaust tailpipe exit, has a nice coating of light grey carbon, suggesting a good running engine and mixture.
My older exhaust pre mod, was much more sooty.
Also, (probably not due to the grooves in the most part) Oil consumption is very much reduced to zero. This is probably because beore I was running Mobil 1 (5w 30) or (10W30) cos 10W 40 doesnt seem available in the UK. I think this was too thin. Im now running 10w40 Amsoil. I am also not getting any in my Oil catchcan like beore. Like I say, this is prob not due to the grooving.
Overall all very +ve, and Im very happy. Recommended.