This problem just started happening. The car runs fine during cooler weather, say 50 to 60 degrees, but when it gets up to the 80 degree mark outside the car really bogs down on acceleration and seems to lack a lot of power all through the entire speed range while driving. The exhaust is leaking somewhere near the engine, I'm not sure if that's the problem or what. I haven't tried to do anything to it yet, I'm just trying to find out if it could be anything specific before I change out the plugs, wires, fuel filter, PCV valve, etc. Any suggestions? Thanks!

An exhaust leak by the motor can cause a burnt valve.
Check the spark plugs to see if the fuel mixture is good.
Check the air filter to make sure the motor can breathe.
Check to see if there are any codes stored in the computer.
If it has been awhile do a tune-up.

zx2's are known for having performance problems in hot temps (typicly 90+) its due to the crap way Ford tuned them

The leak isn't right by the exhaust manifold, it sounds like it's near the catalytic convertor, it's not right at the manifoild where it connects to the engine. I know what that kind of exhaust leak sounds like and I know that can burn up valves real quickly. Is there a way to reprogram the computer to make the fuel mixture run richer in hot weather, or is that something that cannot be changed? The reason I ask is it seems like a fuel starvation issue, it just seems like it isn't getting enough gas when the weather gets warm, kind of like vapor lock on some older cars I've owned.

The exhaust leak can be causing false readings to the O2 sensor which controls fuel mixture.