33 spline axles are a bit of overkill unless you have one damn quick car . My buddy run's 10's in the 1/4 mile with 31 splines . When you change the axles ,you will have to change the carrier to match the spline count on the axles .
My car started making that noise when I installed the cold air intake . If the RPM changes when you spray it with the carb cleaner you might have torn the gasket . If you only replace the upper intake you may have a small piece of the old gasket stuck to the lower intake creating an uneven seal...
Wish I had some intelligent words of advice . I love my parents and in-laws to death , but I think that would be a little close for comfort . Good luck with that !
The harness unplugs from the sensor .There is a metal clip that holds the plug in . You should be able to pry it loose with a pic or pocket screw driver .
I run 31 spline Cobra posi and 31 spline Moser axles . I've had no problems what so ever . My buddy runs the same combo and his car run's 10 sec quarters. If you need to save money , the ford explorers come with factory 31 spline posi units .