What is the difference between the a6 ecu and the a1 ecu. If you were to switch ecu's on a stock engine (adding a6 to a1 engine) with I/H/E and cat delete, what would happen?

 

The amount of fuel and ignition timing information is different on the A6. As well as the addition of the Intake Air Bypass system. The A6 ECU has to feed enough fuel and adjust the timing according to the different cam profile, intake manifold (IAB) and exhaust manifold that the A6 has over the A1.

A6 ECU with an aftermarket I/H/E might be OK. Do you have any way to measure the air to fuel ratio? aka a wideband O2 & monitoring/dataloging software? If your going to start throwing parts and ECU's at your car without going to a tuner. You will need some way to see what the changes are doing to your engine. You need to monitor your AFRs at the very least.

 

So I will at least need to have the timing adjusted?