This isn't relevant to the N55 but for any of you S55 guys, spool performance made a dual FX-150 kit for the S55. This should be good for making some huge power on DI alone.
http://spoolperformance.us/index.php...&product_id=95
If spool makes an S55 retrofit kit for the N55 and makes it compatible with their FX-180 PI will absolutely be obsoleted imo, even though PI really is obsolete as of now but with a dual setup it will make PI obsolete for even high HP users (which is probably the only current application for PI when you are pushing well past 800-1k hp).