Put in new headers, went with 2.5 straight pipe all the way back after install. All is well, save for the fact that the exhaust hits my underbracing when I get on it. Took that piece of brace off for now, but would prefer to have it installed of course.

So! I've ordered powerflex gearbox mount in hopes that will reduce the engine flex enough for exhaust clearance, but I wanted everyone's opinion if that will be enough, or if I should also put in say a lower engine mount insert, like from superpro (trying to avoid nvh as much as possible).

Eh!?

 

What does your upper mount look like?
The 05+06+ gen1 has fluid filled ones....and as they fail...the motor rocks more...and more..and more...

 

Looks good Actualy. Ie been keeping an eye on it, no leaks. I also hve one of those "old style" engine dampers, the shock looking one that bolts to the engine (near the tensioner) then to the frame. That has prolly been "saving" that OEM mount from failure some. But ya, no leaks yet, it does have 100k on it tho!

 

those "dogbone"style stiffeners are pretty good...TSW and VIP made good ones...the later model TSW ones added almost ZERO nvh...shame they are not around anymore(pretty sure)..they sometimes DO need to be rebuilt...but the ends are pretty much stock parts with many different usses if you know where to look for them.
I'm wondering if the mount tore..leaked out...and got cleaned up before you got it...most seem to last 30,000-35,000 miles at best...100,000 miles seems suspiciously high..even for a sedately driven stock car...heck I ripped my FIRST OEM one while still stock at about 35,000 miles......
what you are describing is 100% the symptoms of a failed stock mount....
prolonged driving with a bad mount will wear the lower tranny mount, stress the tranny/clutch, and the exhaust....like you found....