Dont really know how to explain this well, but here goes, when the car is cold and is in park, or when im cruisin at a slow pace and not hitting the gas at WOT, there is a steady "shhhhhhh" type of high pitched whistle comin from my car. If i get under the car, it is loudest right by my rear wheels. I have a new budget Y and a new stainless muffler and piping to the cat. Any ideas?

I have an infiniti g20 and I also get a hissing sound. Mine is my fuel pump. I might have a small exhaust leak too. If its anything other than that I am clueless.

I was hoping it wasnt the fuel pump but it looks like it then, Your the 2nd one to lean towards that possible...expensive fix??

I am upgrading mine in the infiniti to a walbro 190. Its going to cost me $150 for parts and installation. The oem replacements are a lot of money. But the upgraded ones are cheap.

Exhaust leak?