I have almost given up on trying to resolve this issue. I had the ECU remapped by Angle and this helped but there is still a problem.
No error codes are shown so I think that after spending well over £1000 with no real improvements I am probably wasting money on more diagnostics.
I am also running out of options. I have changed out the entire ignition and fuel sysytems and the ECU, MAF and lambda with no improvement.
I had my first look at the Alfa Workshop CD last night and if you go through the tests for engine faults the above covers everything upto the final 2 test steps which are compression check and valve timing advance check.
So I can only conclude I have serious engine problems - but no smoke, noises or misfires or I need a new variator.
My understanding of the variator is that it uses the pressure of the engine oil to advance the timing. From what I have read here and elsewhere, the oil seals leak eventually which could certainly cause a delay or flat spot before it kicks in after the fuelling and ignition have already changed to suit. Whether this leakage could cause the kangaooring on a steady throttle I am not sure but mine starts at exactly 3000 rpm never below and 3000 rpm is supposed to be when the variator starts to advance the inlet timing (again picked up from here and there).
I have read comments that a leaky variator just takes time to fill up at start up (hence the well quoted diesel rattle) but after that it makes no difference. However I am not convinced by this because if the variator can't hold the engine oil pressure properly then surely it can' advance the timing properly and if it leaks in surges not at a steady rate then ...
Hhhmm... I just noticed yours only occurs below 3000 rpm so the variator could be a waste of time unless someone can confirm when the variator starts to affect the timing ? Thinking in terms of engine oil presure again, the variator may start to advance from idle upwards so it could affect the performance anywhere in the rev range ?