Ok I am just getting started on the Tuning aspect. I have built a 383 with AFR heads, cut cam and a Miniram Intake. I have put the 6 speed in and got it running, kinda. I need to know do the after market units like Accel DFI or FAST units replace the factory ECM or run with it. Is it really worth the money to convert or can I start working on a tune for the stock Unit. Thanks, Eric

Depends on what you are after. If you are looking for the most flexibility, I'd suggest replacing your stock computer completely with an Accel unit (my bias, I'm sure others are acceptable. ) as they'll allow much more flexibility as you try to get the most performance from the parts you've paid for.

Not saying it's cheap, but if you are after the best overall performance, replace the stock computer.

Ok thats what i was trying to get at, So the DFI Gen 7 replaces the computer?? All I will need is that for my car to run right and then begin tuning with it. Thanks

If you go with Accel, yes, you would remove completely the factory computer and wiring harness and replace it with the Accel stuff.

From experience the wiring harness aspect is a PITA. GM soldered the harnesses together behind the engine and you'll need to pull out the entire package connected to the ECU and unhook from the firewall on the driver's side by the relays in order to successfully disconnect the engine harness from the rest of the harness on a 91 or 92. Once it's done, the Accel harness fits right back in with the stock routing and the Accel ECM can even be mounted in the factory location with just a bit of fabrication to the bracket.

But the system does appear to be more flexible than having to burn chips.

I have an adapter box from fasttrack performance that let me plug my accel gen6 dfi directly into my wiring harness and retain the stock computer in place as well. No idea if you can still get them though. Site is http://www.fasttrackperformance.com/