Electronic throttle module.

[Lee]

I have recently replaced the electronic throttle module on my 2000 V70. Was running fine but mechanic who cares for the car suggested fault codes indicated needed doing. Replaced and then after about a week car began surging and then would not run. 4 weeks later and many tech. reports to and from Volvo a second ETM put in are now saying that i need a new engine control module, car was running fine prior to all this. I am unsure how to proceed. Any thought?, I dont think that they know what is causing this an its an expensive process of elimination.