When shifting down my exhaust pops and spurts. I am running a power commander with the standard mamp

Why does this happen? Do I need to change the map to a leaner mix

Paul

Boy racers pay good money for this effect!

probably a small air leak into your exhaust causing unburnt fuel to ignite in your exhaust.

Cool innit

Just sorted mine out by advancing overun settings from 34 to 60 in 20kpa bins worked a treet, went from explotions to little pops that sound great. This took me 6 months to sort out, played with fuel setting and overun settings to no avail. GOOD LUCK.