1999 Corolla Whistle at Idle

My girlfriend just picked this up yesterday. Has 113,000 looks like its been well taken care of the engine is super clean, no oil anywhere, new looking belts, hoses, clean fluids. The air filter is white, looks like it was put on recently. After we drove it around for a half hour I let it idle and noticed a slight whistle sounds like its on the intake side. I sprayed brake cleaner all around the intake gasket and hoses, didn't notice any difference in the engine sound. Any Ideas? Thank you

My girlfriend just picked this up yesterday. Has 113,000 looks like its been well taken care of the engine is super clean, no oil anywhere, new looking belts, hoses, clean fluids. The air filter is white, looks like it was put on recently. After we drove it around for a half hour I let it idle and noticed a slight whistle sounds like its on the intake side. I sprayed brake cleaner all around the intake gasket and hoses, didn't notice any difference in the engine sound. Any Ideas? Thank you

Recheck the vacuum hoses and main air intake connections (the clamp may be a tad loose). Also check the air flow sensors are attached tight and are not cracked.

You're certain the noise is a 'whistle'?

99% positive it just sounds like its air whistling. Definitly not a squeal, or whine. The problem I have is the intake is such a weird design I just don't see anything that makes sense. There is only one vaccuum line...triple checked lol

OH, and if the MAF was cracked it would definitly register a code...no check engine lights

Thanks again in advance