95 mpfi 4.3 back fires

hi i have 95 blazer 4.3 , it just started backfireing when you let off the gas it runs fine, has full power . i changed plugs ,wires, cap all looked fine fuel pressure 56 pounds even tried new coil . no trouble codes come up, throttle plate cleaned , you let off the gas and back fires 3 or 4 times in the muffler any help would be great thanx also need info on ignition timing how do you set it , is there a plug you have to remove to check initial and what should it be

I can help with the timing.

Put the IC system in the bypass mode by disconnecting the set timing connector. This is the single wire sealed connector that has a tan with black stripe lead. It is located near the VCM connector in the engine compartment.

With the ignition switch off connect the pickup lead of a timing light to the number one spark plug. Use a jumper lead between the wire and plug or an inductive type pickup.

Start the engine you should know what to do from here.

The timing should be 0degrees BTDC.

Don't forget to hook the IC wire back up.

I will look into the backfire situation for you.

Thank you john , i will check the timing and get back to you . you got a nice 69 , I had 67 ss 350 but blue with the stripes but i sold it and bought 88 iroc convertable , in the the process of putting my vortech s trim on thank you again !