Quote Originally Posted by statesman View Post
So far you've only copied over the fuel/VE/spark tables. You need to copy over every single table in the entire tune file.... including the diagnostic tables.
I think you may be right. I thought I had copied everything across, painfully line by line.

However, I had an hour to work on the car tonight, and thought I would do some simple experimentation to try and see if I can rule out certain things. A post from rcr1978 in https://forum.efilive.com/showthread.php?27605-EROD-Calibration contained an LS3 tune from a PCM with the same OS as mine - 19211212.

I put that tune on my ECU unchanged, and there is a huge improvement. The stumble seems to be gone, the Tacho/ECT correctly read on the dash, and it seems to add 100bhp to the car throughout the rev range. Only done 20 miles with it so far, but seems like a positive step to me. I will nor refine from there to get the fuelling as perfect as I can.

Thank you very much everyone, for taking the time to guide me - it really was hugely helpful.

Martin.