18-20K ??
If they did we would still use them !
The engines used for ages as the standard for Q-500 were the box-stock K&B 8011 and 4011 (torpedo .40 type). A REALLLLLLY good one would turn the MA 9x6 up at 16,000 rpm during the correct phase of moon. It wasn't till a few years ago that NEPRO jumped to the TT40 as a standard. A properly prepared TT40 turns an APC 9x6 on average at 16k - 16.5K rpm completely stock.