turbo spools all the time. On wide open throttle from start, TD05 will build pressure around 5k above. TD04 2-3k above but puff out of breath around 5k. That's where your boost will drop slightly or equalize with atmospheric pressure.

Big or small turbo has minimal to do with FC. Tuning, way of driving and setup yes. If you use big turbo, but never build up pressure, your engine will consume petrol like average NA. If you boost, depends on the tuning, stoichiometry, efficiency of the power transferred and Power to weight ratio is perfect, your FC will be good also. You can hit 5k rpm with vacuum. Controlled entirely by your foot. There are alot of ways to reduce lag slightly. A bit too lazy to elaborate.

Your turbo will spool to build up pressure when its either wide open throttle or throttle opening is big enough to flow into the intake manifold. don't get confused. Pressure in the intake manifold may not be the same as your intake piping. All is regulated by, your BOV, your Throttle body and your wastegate.

Yes. Running up to 1 bar with stock internal for S4PH. No problem. Only problem is traffic jam and you cannot use all the pawa. Monitoring is essential if your setup is half complete. A complete setup will have proper ventilation ensuring the engine bay does overheat, a good management, injectors, fuel pump ensures adequate supply of fuel and injection volume, Good & correct tuning with proper ignition timing, and good boost regulater. E.g boost controller or wastegates.

ok.. here's my take. Most of the points I think i can concur.

Wastegate/Actuator = Controls peak boost. Pressure activated. agreed. Wastegate relies on loaded spring, so peak boost control can change mechanically with spring selection. Actuator has fixed max boost. Change whole actuator only because it's not meant to be dismantle.

Solenoid = yes if the ECU/Management have Boost control capability. If not, most older gen cars/simple setup runs without it. There are simple mechanical boost controller, but it just regulates the boost, allowing higher boost tolerance for low boost wastegates/actuators.

BOV = yes safety valve. Activated when there's vacuum in the intake manifold. Depressurize the air pressure before the throttle body. Agreed on relief valve.

Throttle body = yes, does not regulate turbo pressure, but you do have control on boost via pedal? It does regulate the pressure into the intake manifold and controls the engine rpm & indirectly controls the amount of exhaust fumes out which spins the turbo? if not the boost meter will only register one value, which is the peak boost regardless of which throttle position you put.

I've never pop my vacuum hose. But I've ever pop open the sillicon hose to the intake manifold. If worse case scenario where your actuator doesn't work, your throttle body and your foot will be the last saviour if it does react fast. You either cause some compressor surge or pop the pipeline for the intake system. I trust the Throttle body valve is strong in resisting such force. I've never driven a turbo setup with solenoid/ boost controller mechanism, and would appreciate if you can share more experience on boost controller. But I've driven a turbo car without wastegate.

Just some of my understanding. feel free to correct.

Well we can't deny the fact that engine does effect the turbo operation. 50% throttle body yes. But if the throttle position is lower say 20%, I doubt there will be any pressure build up unless there's very low load. I think this debate would be endless.

Yup I know Preve CFE has a solenoid on the borg warner turbo housing. That too kept me wondering on the reliability. Yup regarding on solenoid function I do agree. But I think it's also because the internal wastegate actuator's spring is not as strong as those external. Slight pressure may open the door results in efficiency drop.

LoL, I think this discussion will go endless. Personal view, I still think in general TPS does give you the power to control the boost in some way until it reaches your peak boost whereby the Actuator does its job. Probably the word regulation is not applicable but by controlling the TPS, you may control the boost coming into the intake manifold if the pressure difference is big. Obviously as you've mentioned, load and engine operation does come in sight in generating pressure, but indirectly it still relies on TPS. (engine operation, exhaust gas etc...)

You hit 1 bar on high speed, then decides to cruise slower, instead of lifting up to shut off the throttle body, you slowly reduce the tps % to reduce the amount of air pressure coming in to the intake chamber. Pressure before throttle body will increase at this point till the BOV relieves or the turbine is relieve by the actuator & slows down the pressure building process. At the moment where the pressure differential is there, your TPS does limit the air coming into the intake manifold, thus registers a lower pressure. No doubt if the load increases, tps % constant, the turbo still building up pressure, pressure before throttle body increase, the pressure coming into the engine will increase because the amount of air & velocity increases. But it does give you the power of controlling the pressure by further reducing the tps. We all know if there's pressure above atmospheric pressure, the engine operation will increase until its overcome by the load.

Just my point of view. Hope you won't hammer me hard again