Example of how to change the product type used in Infusionsoft for Promotions line items.

tw_ee_is_promotion_line_item_type.php

<?php //Please do not include the opening PHP tag if you alreayd have one.

add_filter('FHEE__EEE_Infusionsoft_Line_Item__ext_sync_to_infusionsoft__product_type', 'tw_ee_is_promotion_line_item_type', 10, 2);
function tw_ee_is_promotion_line_item_type($is_product_type, $line_item);
	//If processing a line item and te Promotions add-on is active.
	if ($line_item instanceof EE_Line_Item && class_exists('EE_Promotion')) {
	   	// Check if the object related to the line item as an EE_Promotion.
	   	$obj = $line_item->get_object();
	    if ($obj instanceof EE_Promotion) {
	    	// Set line item type to be 'Special: Product' which is type 12.
	    	$is_product_type = 12;
	   	}
	}
	return $is_product_type;
}