So in the 90 brougham 350, I have heard a noise since I bought it. I can only hear it when the engine gets warm. So I can be at a red light, hit the gas kind of hard and hear a metal rattle. It only last a second and only when I'm in gear(when the engine is under more stress). I dont know what this is but I need help. I was gonna put it in the shop but wanted to see what yall think it is. ahhh, the motor swap and this noise have me worried about my caddies.

Sounds like preignition caused by either a sluggish EGR valve or a bad vacuum signal to the EGR.

interesting. So I just test the egr? what is the long term effect?

EGR is either vacuum or vacuum/electric controlled and is used to bleed varying amounts of exhaust gas into the intake manifold in order to slow down ignition flame travel under load or steady cruise conditions. This lowers exhaust temps and nitrous oxide production for emissions compliance. The vacuum type is sourced from a temperature controlled ported source (no vacuum at idle), so you have to be able to use the accelerator to check the vacuum.

By testing and cleaning the EGR valve you stop the momentary load ignition ping and you just might pick up a mpg or two. If the valve slowly gets dirtier/more sluggish you run the risk of real engine (piston) damage from detonation.

You can completely disconnect an EGR valve, but then the fuel mixture is altered significantly, you have to retard timing, and gas mileage goes down the tubes.

I'm not familiar with your engine, but EGR removal generally involves a bolt or two, maybe a wire connector or vacuum tit. Check that the spring loaded pintle (taper valve) moves freely in and out and does not stick shut. Use choke/carb cleaner and a toothbrush to scrub it clean. Try not to get solvent in the vacuum tit or up the pintle shaft. If you or a friend has a vacuum pump, the pintle should move in and out from 0 to 25" of vacuum. You might have to replace the gasket.