Backfire/popping during acceleration at high RPM

[Whiplash]

I have a '97 RSTD, it normally runs great, but lately it had started to pop or backfire at higher RPM/Speed and I can't figure out what the problem is. Does anyone have any thoughts on this.

I have drained the tank and put in fresh gas and run a can of Sea Foam through it already.

[MiCarl]

Your title says "during acceleration", is that correct?

 

On acceleration it could be a carburetor issue or a spark plug. Try spark plugs first.

 

Deceleration is likely to be an air leak or bad air cut off valves.

[Whiplash]

Your title says "during acceleration", is that correct?

 

Yes, that is correct, seems to happen mostly in 4th and 5th gear... sometimes 3rd... doesn't seem to happen in 1st or 2nd... and always during acceleration... especially when I get on it hard.

 

I will try the plugs and see if that is the issue... I was leaning more towards carb, but plugs will be an easy fix

[Patch]

I agree with MiCarl and like you said plugs are...

 

But this could also be timing, or advance.

Which means it could also be pickup coil; say if it only happens when hot.

Further down the list would be carbon or pre ignition.

 

Would be helpful to see the plugs with the jug numbers posted.. If the problem continues.

 

If you would like to get a good sense of how the engine is doing, take the compression while changing the plugs.