So just ordered my Stillen SC

Z&I

I did exactly this ... wanted to make 500whp.

Upgraded the Vortech Impeller to SI trim and used the Stillen 9 lb pulley ...
It produced 483 whp/ 378 tqe at 11.9 psi.

Grenaded the stock motor as a result, and now I am having to rebuild it.
(Should have built the motor in the first place, it would have saved me time, money, and grief).

Can't say for sure if your stock motor will hold up, but I definitely wouldn't do both the impeller and pulley at the same time...

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gussyturbo z

Do you guys think that the test pipes could cause a little loss of hp? I had cats on it and it seems like it's a little sluggish at times. I'm thinking about going back to cats. Plus the fire balls were pretty cool.

Z&I

Hard to say what is going on with your car without looking at the dyno sheet or test driving it ...
It could be almost anything.

But any time you change or alter something in the power train you are going to affect everything else as well.

Your car might benefit by the back pressure caused by the cats.

I had PPE long tube headers with no cats on my car ...
That combo created an easier exhaust flow with a smoother scavange, but at the cost of increased loudness, emission odors, and perhaps a little drop in torque.

With the tune - my car did have a pretty flat torque curve which all but eliminated the flat spots during acceleration.

Hope this helps...

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gussyturbo z

Thanks man! I guess I will try some HFC. Recommend any? I have the AAM 3" exhaust that helped a lot. When I changed the HFC to test pipes it felt different .