A year ago i decided to clean the intake system on my 156 V6, as the previous owner had some Simota?! ricer open filter on the car connected directly to the MAF which was connected directly to the flexi hose. Appart from the fact that these open filters do nothing but make noise and suck up power robbing hot air, few people realise what detrimental effect shortening the intake on these V6 cars have. The intakes on these cars were torque tuned front to back, removing or changing parts of it will in most cases make it sound nice, but reduce torque. I have since sourced a standard airbox and snorkel, as well as top intake plastic pipe, and the car feels much much torqier. As the boy racer filter also was just resting on the top rad hose/oil cap, a hole was formed in the filtering material due to vibration, letting in crap. Upon inspection inside the intake tubes/plenum i found alot of oil (as mentioned previously, this is quite normal) and signs of dirt in the oil inside the intake. Luckily it seems the oil trapped most of the entering dirt inside the plenum, and there was no signs of damage or dirt further down. I cleaned everything, and sprayed down the TB with carb cleaner without moving the butterfly. The car runs great now. I also cleaned the MAF with electrical cleaner, this seemed to have had a positive effect on fuel consumption and throttle response. To conclude, even though the oil from the breather system causes a mess inside the plenum, it also traps dirt that might find its way into the intake that would otherwise end up in the engine. My advice then, do not clean out the oil in th intake more than once yearly, regularly inspect your entire intake tract for leaks and damage, keep the intake system standard for best performance/smooth running, and regularly replace/clean the air filter and do regular oil changes.
On a sidenote, i replaced the corrugated flexi hose on my car with a nice red silicone unit made for these cars by Autolusso, as the standard hoses always tear at the corrugations, and i fitted a K&N filter inside the stock airbox. The car runs like a dream. For those spreading the rumour that K&N filters kills MAF's, please go do some research on youtube, or directly write to K&N about the matter. They spend alot of time/money conducting tests on this myth, and could not find traces of filter oil on any of the MAF's in the tests. Our MAF's fail at random because of dirt (leaky airboxes) and in many cases due to poor quality materials used in the manufacturing process being subjected to heat and vibration.