This is what I did tonight: I've started by removing and dismantling the entire air intake: first the air filter and filter housing (inspecting each). I then proceeded to remove the snorkel and the vent pipe from the top of the valve cover to the rubber snorkel - the darn plastic cap broke into 3 uneven pieces ... and I have purchased this thing brand new about 2 years ago..
There were no restrictions anywhere in any passage ways. Other than some oil spray in the snorkle, MAF and the vent tube, I didn't observe anything unusual.
I then removed and inspected the EGR valve. It too appeared to be in good condition with a strong spring keeping it normally closed. Blowing into it wih my mouth (hehe) it was barely escaping past the closed valve. Pulling a vacuum on it lifted it up and removing the vacuum snapped it closed quite crisply. Works as designed, I believe.
Next, the turbo: first of all, it spins, but it doesn't spin freely to the touch. Not like the turbo in my 617.952 engine I had before. That 617 turbo spun freely with just a gentle touch. The turbo in this 603 turns when you use your finger to turn it but there is just enough resistance that it will not free-spin no matter what you do. Not sure that's normal or not. There was no play in the shaft.
Here is more info. Having removed the entire air input to the turbo, I then re-connected the EGR valve and started up the car. Again, it started on first crank. I then attempted to reconnect the cross-over valve.... and before I even closed the gap completely the car had stalled! Mind you that input to the turbo was completely open - not obstructed in any way. Still, the engine stalled immediately when I put the crossover pipe in place!
Next, I started the car again, and this time, I had the helper rev up the motor, while I observed the turbo (with a little mirror). The turbo did NOT spin even when the helper revved up the car pretty good - in fact it never moved... I had hoped that it would spin when revved up but it didn't... is this normal?! I do hope the Turbo is ok (though there is some oil leaking past the seal for sure).
So, at this point, my theory is that there is an obstruction somewhere in the Exhaust - probably the catalytic converter (as someone else pointed up above). My reasoning: if the Cat is plugged up completely, the only exit path for the exhaust gasses is to overpower and push past the the EGR valve, and escape out the top of the turbo. That's why the sound changes completely when I pull the vacuum and open up the valve - no resistance to overcome, so the sound changes, but it's still the same escape path for the exhaust gasses to travel out of the engine. Once I close the gap with a cross over pipe, the engine stalls because there isn't enough oxygen to keep it running!? I now believe (looking at that picture), that if the gases can't escape downwards through the tail pipe then they won't travel past the turbo blades and therefore the turbo doesn't spin....
