To find the red plug you need to remove the screw holding the ECU in - by the cars jack - and lift the whole ECU out - the red plug is at the bottom - quite large and hard to miss. If the plug on the head was oily this will be for sure.
No noise from the fuel pump ?? there sure should be but then if it made no noise at all your car wouldn't start.
It will be hard to check the turbo actuator in 'live' operation but you should be able to move it - it is the bit that looks like a tin can with a threaded bar in it - you should be able to move the spindle up and into the can at least - this proves the linkage is OK.
No more than 3000 rpm really does sound like limp mode as a result of overboost in which case you are partly correct it is fuel starvation - deliberate fuel starvation - the ECU does it to protect the engine.
Are you really checking the turbo / air hoses when you say they go stiff when running? especially if you aren't actually touching them whilst A.N.Other works the loud pedal.
There is no in tank filter, leastways not one that is servicable - you need to take the whole pump out of the tank, I think it has a gauze filter on it but it isn't something that you can buy a replacement for.
While we are on that topic - rev the engine from under the bonnet - you don't it is all done by the ECU via sensors on the accelerator pedal.
You really shouldn't be able to feel turbo hoses stiffen especially with no load on the engine - i.e. not driven. You can't really check the MAF visually, unless the wires ar eboth broken but they are damned hard to see - need to measure it with either a diagnostic tool or a multimeter really.
Does this car still have the EGR fitted - exhaust gas recirc? - it could be stuck open I guess.