No issues here either with the Eibach Sportlines. Had mine in my '03 GT since 2003, and before that they were in my old 5.0L for 3 years prior. They still feel the same way they did when i first got them,and the stance of my GT has been unchanged on either corner.
But i do remember years ago Eibach did have a bad batch of Sportlines, but not for long, i'm pretty sure the issue has been dealt with long ago.
As for drag racing with them, lets just say i am running Lakewood 90/10 foxbody struts to help with weight transfer, which is the biggest issue with these springs.
I've actually been thinking about going coil overs for this reason so i can get a good spring rate for both the street, and track use, but yet fine tune the ride height i want.
Other then that, i love how my GT feels on the highway as it hugs the road, and i love the look the Sportlines gave my GT.