Gator SVT,
From what I am hearing the Falken is a good choice for STS/STX. The 215/45-16 offers the best of both worlds, smaller diameter for better acceleration gearing and wider contact patch. The big question is what width wheels will these be on? I'm assuming stock width SVT wheels since it is the 16" diameter you are considering. The sidewalls of the 215's would like a wider rim for better support under cornering loads, but the stock wheels will work fine I think. I have also heard the Falken Azenis tend to run wide. You might want to find out the rim widths that Falken suggests for these sizes. When autocrossing the 45 series tires, in my experience, you won't have to go much over the max. pressure stamped on the tire to get good grip.
Respectfully,
Andy Hohl
