Where did you put this code? It should go somewhere above the main posts loop.

It's currently at the end of the Featured Posts section in the posts.main.php file which appears to be above the main post area but maybe I'm missing something... ?

Try this

if( $Item->ptyp_ID == 1500 ) echo 'Yes, I am really an intro post!';

Thanks Sam2kb - I replaced my code with what you provided and it appears to have no effect.

Then the post is not of type 1500
Use $Item->is_intro() instead

if( $Item->is_intro() ) echo 'Hooray! I\'m an intro post!';

Again, no effect. Not sure what the problem is but something is obviously broken...

Try this

echo $Item->ptyp_ID;

It put a "1" (no quotes) below the post.

Then it's a regular post

Well, the Featured Post box is checked - I've even unchecked it, saved, rechecked it and saved again. Any ideas?

Ok, I see it now. There's a difference between featured and intro posts

Your post is not intro that's why it doesn't respond to is_intro() check. Add this

if( $Item->is_intro() || $Item->is_featured() ) echo 'Either intro or featured post';

Ok, that makes sense. So then what should I replace my original code

if( $Item->ptyp_ID == 1500 ) $GLOBALS['MainList'] = NULL; 

to make it so the featured post is the only post that shows up?

***EDIT***

I'm an idiot.

I should have had it set to Intro the whole time. So sorry to waste your time - I'm retarded.

if( $Item->is_intro() || $Item->is_featured() ) $GLOBALS['MainList'] = NULL;

Man, I feel like a total jackass. I'm really sorry!

no problem