Engine Issue!

[4runnerman]

I know this isnt the right forum for my 4runner but i figure my 4runner is the same as the pickup just different body style. Well here is my issue.... Let me start off that im a HUGE toyota lover! I would never buy anything else! I have a 1991 Toyota 4runner/4x4/3.0L v6. I have been having a wierd noise in the engine lately and i can't figure out what it is. When i put my car in drive and just hold the brake down and let it idle at about 1k-2k rpms it makes a knocking noise in the engine. If i go hold on the vacuum hoses i can feel it in knockin through those! At first i thought for sure it was a bad bracket or value but everyone i have talked to said that it is not either one becuase it is not loud enough, Also that i would feel a huge power loss, which i havent felt. I can't pin point the sound. It sounds like it is right in the engine block. But i dont know!! Please let me know what it could and give me some idea's. Thank you for your time!
Ps. Let me know if you need more info!? or if you have any questions.

[Bakemono]

Exhaust leak?

[4runnerman]

You know what... That is funny you say that. I smell exaust through my A/C. You think thats it?

[rogerman]

maybe your headers are warped or the crossover is messed up.