Modify WordPress Search

You could try something like this below.
Basically, if we are performing a search and it is the main_query (the query that generates the page results) ignore the default search and perform an exact match via the query_where

function custom_product_search_exact_match( $query ) {
    global $wpdb;

    if ( is_search() && is_main_query() && !empty( $query->query_vars['s'] ) ) {
        $search_term = $query->query_vars['s'];
        $query->query_vars['s'] = '';

        $query->query_where .= " AND ($wpdb->posts.post_title="$search_term")";
    }

    return $query;
}
add_filter( 'pre_get_posts', 'custom_product_search_exact_match' );