Ill describe this as best as I can, since its a rather subtle sound, probably hard to capture a sound byte. Heard it on the way home from work tonight.

when pulling through the revs from rest to around 3000 rpm, Im hearing what "sounds" (im using that term as loosley as possible) like a crook injector (to give you the idea of the sound). It was the first thing that came to my mind.

BUT

for the life of me, from inside the cab (as its to freaking dark and cold to do this tonight by lifting the hood) i would swear its coming from the exhaust side of the bay. Im getting a smell of fuel inside the car, but upon exiting, i smell nothing. Could my exhasut gasket have let go in a spot?

anyone with any experience with something similar?

Ill be lifting the hood when i rise at an apropriate afternoon shift hour, but until then fire away with whatever thoughts you have.

might be loose exhaust manifold bolts

Remove the serpentine belt and start engine see if the sound goes away. If it does check for play on the water pump pulley. When the water pump bearing goes the impala rubs on the engine block causing a rattle sound which comes from the exaust side but towards the front.

cheers for the tip joolz, ill remember that.

ive been outside and with the hood up, its definately the exhaust unless there is meant to be gas coming from the join between the manifold and the pipe going to the cat...

I cant really get into a position to check wether the bolts need tightening or the exhaust is genuinly stuffed. I cant imagine why it would let go there, unless the cat was blocked and pressure build up popped it, but i havnt noticed a big lag in the performance to indicate a blocked cat.

can these bolts work their way undone? or does it indicate something more?

more likely to be the gasket has let go between the two pipes. had that happen before.

dont tell me that... thats a cheap easy fix, and thats what i should be doing coz im trying o save to go overseas... but what I want to do is use it as an excuse to put a 2.5 inch system cat back on it...

Is that the Chevy Impala? or the water pump impeller? sorry it just made me laugh.

Mate i reckon it may be your cat. The one on the turbo car let go and it rattled and ticked & carried on like there was some loose bolts or something. Took it off and half of it just pored out onto the carport floor. If you don't have cash for a replacement just punch out all the honeycomb with a jack handle (recommending taking it off the car) but this is ILLEGAL so it not recommended but highly unlikely getting caught if the car is stock looking.

Atleast you knew what i meant!

ha ha!! that was exactly what happened to me when that gasket let go. i drove around saving money for a new system with the car sounding like a mack truck. then i went to get it fixed, and thats all it was...