It's number 3, stick a fork in it! And there will be LESS pressure pushing the air in as you go higher in elevation. Go high enough and the piston won't 'suck', it won't create a 'vacuum', because there is no EXTERNAL pressure in space. And hopefully the fuel makes a 'phase change' from a liquid to a gas, due in part to the low pressure it is subjected to during intake.
By the way, you can't hear a 'blower' scream in space...
Similiar questions:
Is a plane 'pushed' up or 'lifted' up? Are F1 cars 'pushed down' by the air foils or sucked down by a low pressure zone beneath the air foil?