Why won't my 93 geo metro accelerate above 35mph

Hello, since your concern seems to have stared after you "changed the head gasket", could it be possible you've reinstalled the cylinder head without reseting the timing properly? That's my first guess. Truth be told, there's no way you can know what's going on without performing hands on testing. Have you checked for fuel delivery, ignition spark, engine timing, air to the intake? That's where to start checking. Use this link to find some shops near you that can help with your concern: www.repairpal.com/repair-shops