So my 2004 MCS started making an odd noise under full throttle in 3rd gear and higher. It almost sounds like it's begin blocked air wise if that makes sense. I have not had 2 seconds when it's light out to pull the filter out to look to rule that out. The only other change has been putting on winter tires. It seams to still have the get up and go but NOT as much as before. I don't know if that the tires or placebo affect going on now that there is and odd sound. Any advice after I pull the filter on how to diagnose the issue? Oh and I did have a full oil change recently with new filter and the noise is still there.

Thanks gang.s

 

Well I pulled the filter and the friggin thing was nasty dirty. Gonna replace it in the morning and with the oil change the other day it seams to be less loud. So I'm guessing it was a combo of dirty filter and dirty oil.