Too many variables really. Engine condition, driver ability, track conditions, tires, etc, etc. It should be capable of 13's, with the right conditions. Also turboing a B18C5 is more difficult than a GSR. The C5's compression ratio being the main factor. It'll need to be tuned by a proffesional to stay together for very long. You can boost a GSR a lot higher than a C5 on stock internals. I have seen a C5 on high PSI with 430HP, but he spent over $20K building the block, and tuning it to handle it. Still wasn't a very reliable car.