Hello guys,recently my brother purchased a 1995 5.0. It has a few things done to it, aluminum heads,cobra intake,fuel pump,pressure regulator,4.10 gears,long tube headers,solid motor mounts and some other stuff.We first noticed a problem when we raced each other at the track in mexico, my stock 2.73 gears,with long tube gt stayed right next to it all the way through.The car does not idle very well,and it seems like its misfiring but could also be an exhaust leak,we have been trying to chase the noise/misfire for a while with not results.The car has new cap,plugs,and wires.The noise follows the engine rpm at idle it happens every 2 seconds or so and the higher rpm the faster,there's no difference between hot or cold engine. Also i checked timing and with spout out its at 14(we run premium) but with spout in the timing jumps a lot never stable. I made a video of the sound at idle to see if anyone with more expertise could help.Thank you
https://www.youtube.com/watch?v=klUpxvvry6I&feature=youtu.be
https://www.youtube.com/watch?v=6EtcVw-613I&feature=youtu.be
https://www.youtube.com/watch?v=klUpxvvry6I&feature=youtu.be
https://www.youtube.com/watch?v=6EtcVw-613I&feature=youtu.be