I too had top end rebuild with CIS also done but have opposite effect, backfiring (heavy gurgling) on decel whe in gear (ie on a dowbhill) but only until the engine is at full temp and then it goes away..is that a lean/rich issue or an exhaust leak? (77 targa/83 sc engine)

If exhaust and it’s installation is full ok then your mixture at deaccel. at cold engine state is probably too lean.

As you mention a 83‘ engine at cold state the mixture is statically enrichen by the frequency valve.

So check your initial CO setting if not too low and if ok, then check the air sensor plate angle/setting.


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Thanks Andrew

I am taking to my shop for a check and will pass your ideas on