I recently got my Chev Impala (2001, 70,000km, out of warranty) to the selling dealer as the car developed some kind of "air sucking" noise on acceleration (it sounds more like whistling on hard acceleration, pretty loud). It's much like the problem I got years ago with another old car - bad catalytic converter.
But the result is so frustrating. The dealer says they did lots of testing including on vacuum and catalytic converter, but found no problem! They say this could be normal because some of their brand new Impala's have the same noise. So just charged me 1.5 hour labour, that's it.
Taking the car back, the air-sucking noise is louder, and something else is wrong - the car lost a lot of acceleration power! The car used to be very powerful when accelerating, but now it's tough to gain speed, especially getting onto highways. I have to step hard on the gas pedal, the engine making big noise, still quite slow to get speed up. I'm wondering what the dealer do to check on the problem, making the thing even worse. I'm sure, if I get back to them, the answer is still "normal".
There are only a couple of Chev dealers in this small canadian city, I do want to have some advice before taking the car to the other dealer or another mechanic. Thanks in advance.