definetly #2.
Actually, the cam profile and the exhaust closing has a lot to do with filling the cylinder for the next firing.
#3
Piston makes compression going up, if it would do the same down you'd have oil coming out everywhere.
Jeff
00 gt 2.2kb auto
98 gt stock
the answer is 3.....that was eazy.... learned that in high school.... as my auto teacher told us... "nothing sucks.... well women and fags do..." true quote....