Why does my 1996 geo metro lose power after half throttle?

Not much - 1.0L or 1.3L don't got much power.

Hello, this is definitely evidence of an engine performance problem. The trouble is, we and you cannot really tell what area of performance Is influencing an issue here: spark issue, fuel issue, air intake issue or exhaust restriction even. Testing is needed to find out what area or areas are causing the trouble. It is too difficult to guess at all the possible causes without any direction.