Using an e/t to estimate horsepower can be wildly inaccurate simply because you may be driving the car like crap. If I jump in there and we do the same test and get a 20 second e/t did you just lose 50 horsepower? No, you just lost a driver... Now, when you account for thirty years of use and estimate a 15% parasitic loss of power through your drivetrain, your 100whp calculation seems realistic. If you want a more accurate figure, pay 9.50 and get the car weighed with you in it on a certified scale, then download a dyno app on your gps equipped smartphone. If you want more power... I defer to greater knowledge contained here:
http://forums.hybridz.org/index.php/topic/95316-braaps-l6-efi-induction-advice-and-tips/
Take a deep breath and read that a few times, in its entirety. Refer back to it when you get stumped, and dont be discouraged, horsepower is just a number.