If you are worried about cost, try to find a good chassis dyno. We went to a local shop and you can have a day for $125/hr. Flywheel HP is nothing unless you can deliver it to the rear tires. Like Jim said, its a tool that can be utilized to find things ahead of time to help you better your ET by utilizing all of the power your making. We dyno'd our car for the first time this year and found that we were running out of the engines power range and found that the timing was out of wack. After the dyno session, we change the timing and went to the track. We picked up a tenth. Its worth it and its good for selecting the proper converter for your car. just my .02 though