I'm running dumped flowmasters and i'm loving it. It just drones a bit more in the cabin. As for what you should be running, i'd say a high 13-low 14. You need to get some gears.
I have magnaflow dumps and I like them a lot. If you get some gears and some tires you should very easily be in the 13's. more than likely mid to high 13's.
When I got my Kooks longtubes and 3" O/R X-pipe, Higgins put a pair of dumped 2 chamber Flows on my car. I hated the drone and took them off after 2 weeks. I replaced them with dumped Dynomax Race Magnums, which I love.
When I got my Kooks longtubes and 3" O/R X-pipe, Higgins put a pair of dumped 2 chamber Flows on my car. I hated the drone and took them off after 2 weeks. I replaced them with dumped Dynomax Race Magnums, which I love.
i have the race magnums on my 1990 GT and they are awesome. they aren't "too" loud at idle, but they get loud in a hurry under WOT. i noticed that they don't drone like the flows do when you dump them.
As long as they are after the after-cat o2's, or after the pre-cat o2's if you have the rear o2's disabled or MIL elimators they won't hurt anything.
But unless you are making plenty of power the lack of back pressure would be a low-end torque killing thing. And no 4.6L needs to lose any more low-end torque. You would make more power at higher RPM's in that case though.