Quick summary:

T2 is a standalone aftermarket engine management system that can be used to run any supported trigger pattern 4 cylinder engine. It is not 'plug and play' into any Ford car and will need a wiring loom making to incorporate as a bare minimum crank sensor, air temp sensor, water temp sensor, throttle sensor, ignition output and 4 injectors.

P8 is the standard ECU found in large turbo escort cosworths, few people who can actually live map the P8 system in the whole country: MSD, Ahmed Bayjoo and perhaps a couple more. P8 runs closed loop fuelling as standard and also runs closed loop boost control. Not quite as 'robust' as a L8 as the adaptive ROM that controls the closed loop fuelling can f*ck up and cause overfuelling problems.

L8 is the standard ECU in a 4x4 Saph and is really the 'preferred' ECU for most. Can be live mapped by a few more tuners, has better processing speed than the L1 or L6 and runs a knock sensor. It is great for most as it isn't as succeptable to 'noise' from poor earths etc. as the P8.

The L8 runs a baby board as standard which is a circuit board about the size as a cigarette packet and carries the EEPROM chip. Some tuners only have the ability to produce chips that work in a Pectel encryption and therefore require you to change to a Pectel baby board.

The P8 does not have a baby board as standard, but again, for some tuners to 'chip' these ECUs, they require a Pectel baby board to be fitted. Sometimes this can be to run additional features such as water injection or ALS.

Any clearer?