I have a megan racing header.
When I first got it there was a whistling sound from the flex pipe (leak)
I had a new one put on and all was fine
Now where the tube connects to the flange (on the block) has a crack in it.
so I'm going back to stock.
If you have a manual tranny, you'll definitely notice a difference
I did notice a nice difference starting midrange (4000RPM's and up).
But not I'm going back to stock.
So anyone who has a stock downpipe I need it.