It's good stuff just testy. If you have a good high-quality header, the wrap and header will work well in unison, if you let the car sit a long time, moisture can build up, but if you drive it every day, the heat will burn the moisture off and you shouldn't experience too many rust issues.

HOWEVER, if the header is of low quality (cheap metal and welds) the wrap can disfigure or crack it or cause it to overheat and risk warping other metal parts of the engine. Proper overlap is KEY. I read a review from a WTCC race where due to incorrect installation, the wrap was the only thing holding the header together at the end of the race.

But you should notice a slight bump in HP as the car normally heats up. Higher exhaust velocities and less heat sinking in the engine bay are always great.