Testbook cant retime the injection pump,I think what he is referring to is its ability to raise or lower the idle speed slightly.This is to help lessen the trim vibrating so much when that horrible lump is waiting at the lights....
Its not really fair to compare Testbook with any of the others as it was designed primarily for dealers to setup and diagnose LR,Rover and MG products to factory spec.Which it is actually very good at,and is very reliable.Mine has worked daily since I bought it in 2003 - nearly £10,700 with the Vat...It has always been portable,does not need to be on its trolley.The trolly is usful in a busy workshop as it holds the printer and all the extra kit that Tesbook comes with.The full kit has lots of extras including a pressure/vac transducer,car length multimeter probes etc.
Functionality is quite good,having a basic scope function,graphing multimeter built in.With the right cd's you can programme any new and many used ecu's.More than most people would want,and more money too.
The main advantage beside price for the Nanocom is that it will code Disco 2 fobs from the number inside and switch off ACE etc.They are useful functions in the workshop,but I guess most would only use them once or twice.
Think that is what we are trying to put across to this guy, seems he is dead set on this Omitec kit which is based on T4 as far as i can see but not T4 if you know what i mean. Why he doesn't just get a Nanocom i don't know.