I used a Vacuume guage as pictured below. You can buy one from Auto Parts stores.
http://www.harborfreight.com/fuel-pu...ter-93547.html
I removed the driver's side Pre-Cat O2 sensor. I attached the rubber grommet through the O2 sensor hole. If you leave it there too long, it will burn the rubber grommet.
Reading was over 4+psi at idle, and way off the scale (10+psi) at 2000rpm throttle rev.
Based on the "How To Articles," stated the backpressure
should not exceed 2.5 psi at 2000rpm rev.
The Cat Canverter is clogged. Made sense. I cut out the CatConverter. The honey comb on input side was broken up in chunks, and the rest sure looked clogged up.