Issue with WP_Query (need a array of selected ID's)

which gives me all posts inside the tax inspiration - I need to alter this, so that I get only selected ID's in my array, ex. 4714, 3608, instead of all terms of the tax.

I'm assuming you mean that this query gives you all posts inside post type inspiration and you want to pull specific post IDs instead of all posts of the post type. Taxonomies and Post Types. are two different things.

Try to alter your query to something like this:

$loop = new WP_Query( array(
    'post_type' => 'inspirations',
    'post__in' => array( 4174, 3608 )
));

The difference between this and your original loop is that 1) There is a post type defined and 2) post__in has 2 underscore where yours has 1. I removed the posts_per_page parameter as this query should only return 2 posts.