Help... Huge Loss In Power...
 

Car sounds completely different at start up... almost hollow. RPM at idle are 700... Car is not putting out as much exhaust and is much quieter at idle and under load... very weak on acceleration...

Tell us about your car the year, mods, the past problems, how many miles are on it etc. Anything you can think of mechanically. Otherwise we're shooting in the dark.

dose it shake, any recent maintenance? we need more details

01 Bullitt... Longtubes... OR-X... 4.30 Gear... Ran great until this morning...

Also has a weird sound (like a train click clack) when I let out of the throttle.

Spun rod, Timing chain tensioner, maybe a collapsed lifter but I doubt it, bent or broken rod or pin.

Where you racing it the last time you drove it, or recently getting on it hard?

Could also be a problem with a clutch pack if the rivets broke free from a worn clutch.

RPM sits at 700RPM at idle... no longer 1000. Yeah, I got on it yesterday. Doesn't seem to be the clutch pack. It's a completely different sound at start up now.

When the ignition fires is when there is a big sound difference. (the first noise you here when you crank the key)

Why was your idle rpm so high, at 1K? Is that common with longtubes? Mine only idles that high when it's cold, when warm it sits around 750, which is common for most cars.

Not sure, mine sits between 900 and 1000RPM.

You may want to check your spark plugs/coils first.

Mine idles around 700-750 as well. Any CEL? I agree checking the plugs too. Maybe you blew one out. Make sure they are all snug. If that was the case you should have a missfire code though.