Are you saying that the engine revs but the car doesn't accelerate as it should? That's a slipping clutch, it usually makes itself known in first gear as you describe.

Hi the whole subject about cars is based on one factor wear. when cars are new the metal surfaces are raw the actions of use produce wear. this wear eventually reduces the power out put so much so that by the time it reaches it's 8th birthday even if maintained with oil changes and oil filter changes the modern car engine is at the end of t's working life. hence why event extended warranty companies will no longer support further cover.

Sounds like your clutch is about worn out and slipping.

clutch is slipping

First gear starts off fine, but when I rev the engine and release the clutch, it doesn't quiet catch on and accelerate much.

This only happens in first. Second and third take in the power to the wheels just fine.

I drive a mustang 04 3.8 v6 base