Head gasket least of your concerns...over boost/creep could lean you out and knock is what will crack your pistons. Valves shouldn't be an issue.
The 3 port boost controller should help but you need a "pro tune" to maximize function/response. Believe me you will run better and car will be happier with a legit tune. AP base maps are lowest common denominator and only get you in the ball park at best. As it sits the GS unit is probably part of the problem without a good tune.
Good luck.
-DT