My buddy's 01 s2k was having miss firing issues. And we took out the injectors and sent them to injectorx and they cleaned them and sent them back within 2 days. You can see in the pic before and after and the injectors were really dirty. So if you been having miss firing issues and if your s2k has close to 100k miles or more then look into injector cleaning. I'm thinking one of the previous owners must have used 87 octane instead 93.

 

IF my valve adjustment doesn't fix it , that's my next step.
Got my misfire right after using injector cleaner so as odd as it is I think it may be the issue.

 

ive seen this problem before...sometimes the injector cleaner cleans all the gunk in the lines which clog the injectors.