Here is a video:




Thanks in advance, any ideas as to what I should start looking for first?

 

It sounds like an exhaust leak to me.

 

would exhaust leak cause a slapping sound in the engine? It broke the top plastic cover on the engine.

 

why dont you stop running it and pull the plugs and look at the pistons

 

Yeah, if something breaks that plastic cover you might want to look under to see why.

 

Sounds like you got a plug that came loose or blew out. WOW! That 100 shot of NOS actually did blow the welds on your intake....

 

thinking same thing. or a coil pack blew up or something

 

This.

Also, change your oil every 3000 miles. I don't know why you'd think any different.

 

I change mine every 5k, filter every other change. Strong for 110k miles now. Oil change intervals aren't OP's issue here, he has something mechanical going on

 

4 screws to take that off yet you would sit there and run it hahaha. Ok your spark plug is not in the threads anymore you may want to check that. 30 seconds to find the problem see the cover moving with the exhaust noise....

 

I am amazed this thread (and video!) was created before you took the plastic cover off to see what broke it...

 

Don't you like the sound of lawnmower?

OP: Don't run the car until you at least check the spark plugs. It does sound like a giant exhaust leak.

 

I was about to say no sound coming out from the tail pipe.