you forgot:

bearings
Pipe choice
Fuel choice
Tire choice
Manifold choice
Plug type
Gaskets
length of fuel line
length of pressure line
Flywheel
Clutch shoes
clutch springs
air filter type
air filter oil type
engine tune ( especially idle )
Epa settings
exponential settings
servo speed settings

the list goes on and on really...thats why when one guy says I got 15 minutes of runtime, or I cant get more than 7 minutes of runtime it means nothing unless every single aspect between their vehicle and your vehicle is identical..you should know this better than anyone Mark