In the 4.6L forums on this message board Spec has a bad reputation.
I hate them because they screwed me on a warrenty deal. I had a Spec clutch go bad on me after having some problems with my cable clutch setup and exhaust not exactly working well together. I called Spec and asked them a bunch of questions and ended up with a solution that was suppose to work. I did exactly what thier tech guy told me to do (this was before I had my manual trans ASE cert) and it ended up burning out the clutch disk in short order.
So I call them up and talk to them and they tell me to send it in and they will look at it. I get a call from them about a week later and they say they are going to give me a 50% warrenty and I will have to pay for the rest. I say ok, thats fair enough for me. Instead what they do is they charge me more then I payed for the clutch originally and then charged me for shipping back to me which they said they would not because it was a warrenty since I payed to ship it to them.
When I finally get my new clutch disc I was in a hurry to get it all back together. The reason was that my car was on a lift at my local junior college where I was taking an auto class but I was long over due to finish the project and my class was over with because I had to wait like 2 weeks for my parts. I didn't inspec the clutch disc. This is where it sort of becomes my fault. I tried to stab the trans after mounting the clutch assembly to the flywheel and the trans just wont go in. I tried to force it (like an idiot) and cracked my bell housing. So I go to a junkyard and buy a bellhousing local for like 75 bux. I put it in the parts washer at school and when it comes out there is a FAT crack in it. Take it back. He sends me to another junkyard and I finally get a good bell again. Waste of another day.
Now I inspect the clutch disc and assembly and I find that the splines on the clutch disc were burred to hell. They didn't properly finish the splines on the clutch disc and thats why my trans wouldn't slide in. I didn't have time to get the clutch sent back and they provably just would have screwed me again so I ended up filing down the burrs and installing a warped clutch disc which drove like crap.
A few months later when I had some spare cash I bough a new clutch disc for the 10" 5.0 flywheel I had (which was good and cheap) and pulled the 10.5" stuff out. I didn't get to use a lift that time. Did it on my back, in my garage.
So basically a clutch disc and flywheel ended up costing me more then 500 dollars. Do I hate Spec ? YES. Will I ever buy thier stuff again ? Hell no. And to this day a lot of guys on the 4.6L forums are still complaining about Spec quality so I doubt they have got any better.
Was some of it my fault ? Ya sure, I admit that. But I learned my lesson. Always inspect parts, even brand new performance parts.