Your engine bay looks great! I'll throw the front brace and rear stabilizer on down the road... (a short road, I hope!) I may do the TRD springs first. I don't like the flex/float/front push when I get to pushing the thing in spirited maneuvers. Do you ever notice the tail wanting to come around when you get a little TOO lively?
I am also interested in getting under it to study the plumbing routes, etc... I suspect a high-flow cat won't disturb the flow/balance in the Toyota plumbing but might breathe just a tad better with the new intake and TRD tail. It's probably worth a try and so long as I keep the diameter right, can't hurt.
BTW, I was born on the 4th. Something about us Taurus'..... we are forever forever tinkerin' with stuff, huh?
- crisp