zx problems

i have a 92 300zx twin turbo upgraded to bigger turbos. it runs fine when the engine is completely cool, but once it warms up my air/fuel gauge tells me its running rich and the engine starts hesitating. my car doesnt overheat, but it starts smelling like antifreeze and my exhaust doesnt blow out any kind of smoke. can anybody help me understand why my engine hesitates once the engine warms up?

Headgasket, is a possiblitiy. Also check your plugs could have the wrong heat range in or just the wrong plugs.