Just to clear up some items.
Level 3 is for independent Service Centers and OEM customers who may need to match an ECU serial to the engine serial. it will read all log files the same as a Level 2. Sale of the level 3 is restricted.
Level 4 is factory only and only a few distributor personal have access as it is used to program changes in software within the ECU. No sales of level 4 are permitted.
For all others the level 2 is all you will even need. it will read all the BUDS data information and can download all log files. Level 2 is what all service providers require to do the annual/100 hour inspection where you must view and clear fault codes from the injected engines.
Cheers