The turbo seals aren't perfect seals, especially if the engine is off. There are all sorts of weird things that can happen with turbo seals. For example, if there's excessive engine crankcase pressure, some turbo designs can cause the oil to not drain properly out of the CHRA and instead leak out of the exhaust if exhaust backpressure isn't enough. I don't like the idea of any oven cleaner leaking into the CHRA and with the foaming action and whatnot, being agitated into the oil. Disconnecting the oil drain line would probably be a good idea and doing an oil change after a mile wouldn't hurt either.
When starting the engine back up, cranking the engine (with the oil drain line off) with the injection pump fuel shut off solenoid disconnected (to disable the engine) can flush out the CHRA. This is just my personal guess on what to do, I haven't read opinions elsewhere. I would also take full safety precautions when working with oven cleaner that has lye or other caustic stuff because it can blind you or cause chemical burns. If you have a moment of tiredness while working on the car and accidentally point the spray nozzle the wrong way, you're done.
Also, post moved to mk4 technical section.
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