The method I proposed is a really good "cheap" way to just clean the injectors. The pro to taking them out of the engine/fuelrail is that you can reverse flow them. Hooking up something inline without the fuel pump running with the engine running, only "sorta" cleans them in my opinion. That method you are banking that all the debris and blockages are soluble in a solvent solution. This might be true for most debris, but I don't think for all.

Ever take a fuel filter out of a 100k+ mile car and strike it hard with gas coming out? You'll see it is very dark/brown sludge that comes out. It's basically dirt! Things of this nature cannot simply be dissolved running one way through the injector. Same type of filter element that is in the fuel injector screen.

Flow matching is very important because the DME has to guess which injector isn't flowing correctly by O2 sensor readings and timing. Then it makes adjustments to try and match everything.

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2003 BMW X5 3.0i -- MT5, 3.64s final gears, H&R lowering springs, K-Mac bushing kit
2007 BMW X3 3.0Si -- MT6