Most all manufacturers of gas valves have a pressure drop of one inch wg
you mean a valve cover gasket i think
10 foot pounds
The first thing that comes to mind is a blocked PCV valve or the line going to the PCV valve.
All the way. It may be dangerous to throttle your gas flow down using the tank valve.
look along the valve covers on the heads, there should be a small pipe that when pulled seems to go no where, that should be the PVC, it is a simple fix
$32.75 from autozone for a twin cam
In 2012 about $40
It should be between $17-$24.
If you do not feel comfortable doing it yourself, ask a plumber or HVAC tech. It is not an expensive or difficult fix. Price of the valve and a service call should cover it. Shut the boiler down a few hours before he comes to allow it to cool a bit before he drains it will help.
Depends which species. Usually the size of its eyes.
between 250 and 400
If you are not sure where the heads are I wouldn't try to get to them. Generally speaking though the heads are underneath the valve cover which should be very easy to spot and generally is only a few bolts. But be careful because once you take that valve cover off you are in dangerous territory, if you scratch up a head or drop shavings in it or pretty much do anything to it you can seriously damage or destroy an engine.