The diagnostic messages don't necessarily dictate practice, because when they start coming up, there's a point at which the impact is minimal, but of course, push it too far in the wrong direction and things will deteriorate! Obviously given the nature of these things, detrimental effects increase exponentially with degree.
Now, while corvette is wiping his nose, I got home and jumped on the laptop to see what was possible. Using AlSi block and headers, it's definitely easy to push out something with, well, less impact on the hip pocket. Actually, I'm still yet to work out where all that extra money in Corvette's block came from, given the production units are identical:

- Engine.png (910.61 KiB) Viewed 7063 times
What I do know is that I hardly touched the quality sliders. I think the block has +2, the injection and fuel system has +1, and the exhaust has +4. The essence here is that the engine is significantly oversquare, the cam profile is set very high, as is ignition timing. In terms of numbers it's equivalent or superior in most ways (except reliability, mostly due to slightly longer stroke probably), but in reality, the high cam profile is what creates that bump in the torque curve, which I'm not sure is absolutely optimal. Dropping cam profile would help, but of course, reduce the maximum output. Oh, and I used performance filters instead of standard filters, because it didn't have any impact on reliability.
So what I'm curious to know, is how this engine would stack up with yours, actually, in an otherwise identical car. Does it make any difference around the track? I'll attach it if you're interested.