Some questions after HFC install
 

After being able to get the stock cats out and the FI RHFCs on, i have some 'issues' that I have came around, especially in reverse!
09 7at

I did have to unbolt the Y pipe- and eventually had to rebolt the whole catback from the cats to the back mufflers so everything will sit norm again.

The rattles like to come around randomly and goes away when stopped. Rattles for sure in reverse. Cruising is as quiet as stock cats.

Vibrations/rattles! I have found the first suspect which is where the midpipe sits. After a quick wrap and wedge, the midpipe rattle that was hitting the brace was out.
License plate rattle was fixed with a quick wedge of rubber.

This last vibration is happening to what I feel like is under me- at the cats. I dont see anything touching. The brace that held the stock cats was removed due to not being able to fit with the o2 bung in the way.
BUT one problem i had is where the 'demon bolts' are, two top bolts. After many cuts and bruises i managed to get the nut on the other side. But now all i can do is turn the bolt tight enough to when the nut on the other side starts turning with.. which is tight... but not as i want them to be. Ha.
Squirt bottle test shows no leak at the demon bolts, both idle and slight rev in park. Everything else to the axled is goodtogo.
No check engine.


When going from a stop, it feels hard. Which is around 1.5-4k when the exhaust sounds the loudest before smoothing out to a mellow vq rumble.






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Since no input yet.. i went back under.

Hoping that everything has now settled with the new gaskets all around during the install, I went back down and retightened all the bolts from the cat to the back. Tightened the demon bolts down from the top. T handle clamps for the stillen intakes are a savior. Went for a drive. Vibrations still in the cross bar area for the midpipe.
I went ahead and removed the ARK midpipe and wrapped where it comes close to the bar. Snug fit but now it shouldnt be rattling metal on metal.
Startup sounds much more normal.
Park vibration is gone.
Parking with AC ON vibration is gone.
Reversing vibration is gone.

Driving has some vibrations in the throttle.
Completely stopped at a light in drive. The worst rattle/vibration than before!

Where else could it be hitting? I will usually just ignore it since my rear is gutted, but i have some free time



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Check the "W" (tunnel brace) where the midpipe of your exhaust is.

I had to make some adjustments after hfc install as it changed the angle of the rest of the exhaust just slight enough that it would make contact with the brace.

Also check heat shields around the exhaust and adjust for extra clearance if needed.