[Ringoosmeg]

Claass 66 are only designed to do a max speed of 75mph, class 66/6 are lower geared and only do 60mph.
They would not be suitable for passenger workings in general use (ie ok for specials) as there is no ETS (or HEP) supply, the 67s do have HEP.
If the locos are shut down, this will cause a loss of air to the brakes over a period of time, also no anciliaries will run , such as heating, lighting will cause the batteries to become flat, and if you drop out the BIS, you will loose the lights anyway, yes theyappear to be noisy, but in truth they are no noisier than other locos, and the noise you can here is actually the comppressor, under load and then unloading (thats the "ying ying"), the compressors cannot be isolated, as they are a direct drive from the crankshaft of the engine.

66 951 and 952 are both lower emmission locos , built the EMD tier 2 spec, which conforms to the UIC regs, the tier 3 locos (which havent been built yet) will comply with the latest european & UIC emmissions regs.
951 and 952 are both Freightliner locos, and can be identified by some differences to the construction, yes there is a third door in the engine room, this is because the cooler groups are larger to cope with new emissions and therefore the space envolope in the cooler group access is very restricted, hence the exyra door, the cabs are very slightly different too, having the Scandivanian side two pice windows.
The latest batch of GBRF locos which arrived a couple of weeks ago, are alkso to the new Tier 2 design.