You sure that's a Stahl header in the bottom picture? I'm betting that's a Hooker 5303 header. I have to walk out and look at my header to say for 100% sure.
Also, I've found power with that Hooker header and a 3.5 inch collector.
Finally. I've been trying to figure out the make/model of the headers I have on the car, haven't had any luck. But once I had pics and a model # it was easy to confirm.