http://www.gz250bike.com/viewtopic.php?t=769
Looks like you bought it from Astro.
Glad it all worked out.
If he drilled holea in the exhaust, I doubt he did much more "custom" work. You may want to take a look and see that he didn't alter the air filter any. You can do that by checking under the seat or by removing the left hand side cover.
Nice bike.