Normally DPFE hose(s) coming off and loss of power would be a sure sign rear pre-cat is plugged. This would be covered under emissions warranty for 80k miles (US), 130,000 km (Canada).
In your case however, it would be highly suspect that your cat mod has caused the problem.
p.s. A more descriptive heading would perhaps have attracted more attention since all members initiating a thread in the Troubleshooting Forum generally need help.
Edit: Having now read your old thread, sounds like you should re-install old main cat and get pre-cats checked/replaced at dealer under emissions warranty.
Last edited by horseydug; 07/07/03 08:57 PM.