Mike

If it is rattling going up hills, that means it's detonating. There is a reason they call that the "death rattle". First thing to check is timing, your total advance should not be more than 36-38 degrees. Static timing should be 4-12 degrees depending on set up. The next thing to check is for a lean condition, too much air not enough gas. This could be caused by a vacuum leak which could also cause the high idle. You mention the car has 400 hp, if it has over 10-1 compression you will need the best gas available, if it has over 11-1 you may need octane boosters or racing gas. Less than adequate octane will also cause detonation (pinging).

I found the Edelbrock tech support people to be very helpful and you can check their troubleshooting tips at their web site. http://www.edelbrock.com. I had some questions and sent them an email, they responded within a couple days and their advice was right on the money. If you send tham an email, provide them with as much information as possible.

Hope this gives you some things to check. I would recoomend that you not drive the car much until you get rid of that rattle. It will eat a valve or piston before long.

PAt