I have a 1991 350 SDL with 145K miles and a rough idle and injector knock condition. This occurred after the seals on top of the injector pump to the injector lines were replaced. Shop says the problem is not a result of the seal replacement.

I went to the "experts" on fuel injection in my area (Tampa Bay) and they said the injector pump and injectors should be replaced.

Strange thing is that on occassion it runs fine without the rough idle and knock, it is however always rough and noisy with injector knock before it warms up.

Would replacing all the injectors be a first good step in attacking this problem? I think the injectors are in the $30-40 range each to replace?

Thank you.