Being a conversion van its possible for them to move them probably where they'd like but it should be under the drivers seat. I cannot remember off the top of my head if that year has a bcm and a pcm or just the pcm. A bcm is a Body control Module and controls just what it sounds like- power windows, locks etc. I don't think GM did that yey in '93 but I'm not positive, sorry. If you don't find it let me I will help track it down. If the conversion company is still in business they might be a source too.
It should be on the front of the intake manifold directly above and behind the water pump.
Yes it will bolt right up to it.
The fuel lines around the filter; you will need an adapter.
The EGR valve on your Astrovan is on the backside of the intake manifold just under the throttle body attached by two bolts. After installing a new gasket be sure and torque the BOLTS to 17-18ft lbs or the NUTS (if yours has studs) to 15ft lbs)
.043
.43L. 1000ml=1L
Don't know what year you have but some sensors are temperature sensitive and you should run a 195 degree thermostat.
4L60/E l
43L of 18-k gold
remove the intake hose and the exhaust port screwed into the egr valve, the remove the two retaining bolts from the intake and clean any old gasket material away. if possible run a piece of wire down the hole to make certain the passage is clear of carbon build up
There is one before and one after the catalytic converter.
There is no adjustment required, but you can clean it with a carb cleaner.