Just got dual 2.5" exhaust with highflow cats but no mufflers.
when I let off the throttle it cackles and pops really loud.
My question is do I need to take timing out or fuel or both to stop this? Is that sound caused by excess fuel in the exhaust? Is this just a total lack of backpressure thats causing this?
Can I tune this away?

 

Well its a combination of fuel being burned with to little timing,to cure the problem i would enable the deceleration fuel cutoff or raise the timing at the points of noise.

 

too little timing?
I was thinking it was too much
I cant use the decel fuel cutoff because I just changed from the 730 to the 7747 and I have not had time to change the VSS. Looks like I need to take the tailshaft off to do it. In the mean time I was looking for a way to program the DFCO manually.
I will try to add some timing and take out some fuel.
I also just discovered that my header bolts are loose so that might help too.

THANKS

 

NP,hope it helps .
The more you advance timing in the low kpa you will be quieter
because you are firing before the exhause valve opens therefore
quieting the tone.