I thought only the 173 ECUs had the higher top speed limiter but after reading through the LONG Vir thread, I saw this comment by Vic:
http://spece30.com/component/option,com_kunena/Itemid,86/func,view/id,16563/catid,16/limit,10/limitstart,50/
Are there other ECU options beside the 173 that will be OK for top speed?