5 weeks after my last post I can report the car is running much better.
I ordered the two TPS units but they never arrived!
Turns out we forgot to pay for them by bank transfer. Did that 2 weeks after ordering and then waited another 2 weeks but no TPS's.
Gave them acall and turns out the bank details on their Website were incorrect so once sorted they sent me 3 TPS's for the price of 2. This made them around $25.00 each! Holden charge around $240.00 and my local parts man around $120.00. I think it was a good price but lousy service.
Threw it all back together yesterday and started it up. No different. Coughing and back firing still. I've checked and e-checked all sensors and the wiring.
I took it out and gave it a good thrashing and it's going much better.
My theory is it fouled the plugs sufficiently that it would run but as you cracked the throttle open they broke down. It was fine once on boost and going.
Each time I drive it, it gets better.
I'm planning on storing the car at my in-laws over winter so my garage is free for me to get on with my next project, so come Saturday the garage will have a new inhabitant.
At one stage I was so discusseted with it was I was ready to give it away.
I'm so looking forward to a factory engine with great drivability and reliability.
I love working on cars but I hate having to fix them.