When I put a certain amount of pressure on my accelerator during lower gears my car whistles, it has me baffled because it only happens when I'm going less than 45ish MPH. Anyone have any suggestions? If I hold the same pressure while it'* whistling it will continue to do so, until it changes gears than I have to release some of the pressure for it to do it again.

Where does it sounds like the whistle is coming from? Engine bay, under car, outside, inside?

I have a whistle in mine..but that due to a header leak at the collector. GRRRRRRRR

Could it be your intake? Check your filter.

It'* not my air filter, it sounds like it'* coming from the engine though.

A vacuum leak will tend to whistle more then a exhaust leak, but the exhaust can whistle as well.

Why would it only happen at certain pressures of my foot on the accelerator and not at higher speeds..

If it'* just a small crack it may only open at certain amounts. You might have to wiggle the vacuum lines a bit.

Where are they at, I've never had to mess with a vacuum line before.

See if this helps.

https://www.gmforum.com/t278867/

I don't have the L67, is it generally the same set up still?