Ill have to disagrree about the post stating you dont have to or shouldnt adjust the accel option: The the instructions specifically state some tuning may or may not be needed in this area. FOr me, at 0 it fell on its face: At 6-8 it runs/accels fine (I have the single, 4 system)
Thats why the option to adjust accell to begin with is even availble in the advanced options
But lets go back to basics. You need to drop the tank to inspect. Dont depend on just removing the fuel sender unit and taking a peak. You cant see whats going on I did exactly that: It didnt look bad at that angle. Until I dropped it and looked in the fuel neck: Besides the big flakes, the fine brown particles will clog any filter in almost 0 time. And cleaning them out and reinstalling just doesnt work, The scale comes back quickly
OEM style tanks arent that expensive Shop around and you can find them delivered for $220
Like myself and some others said: My money is your old tank is just full or particulates
For those that dont beleive in EFIs: I has the proflo eddy brock on a 502, and now a FAST on my 440. They are absolutley the easiest things to run and tune. The only trick is the installation (routing fuels lines and fuel pump installation location was the worst for me in both cases)
The 502/502 I had with the eddy proflo was blinding fast, responsive and would start in any condition with just a click and roar. It was in a 68 Corvete coupe, 3;55 rear, with Kielser 6 speed. It was plain dangerous off the line, and the power band was everywhere in the rpm range. Originally I had a GM low rise dual plane on it with a Thunder AVS carb. I could never get that carb right: I went thru every jet, all circuits, and accel pump adjustments: I could never get the lag out of it. EFI completly eliminated it. And up here I live at 9000 feet ASL. Try driving a carb tuned car at that altitude, and drive from that down to 2000-sea level with a carb
The FAST is just about as good, I just wish the distributor was keyed with it as the proflo systems are
Eleimate the easiest most obvious probs first. The tank is easy to drop and reinstall
I found that attention to detail to instructions is key as well, and dont take any shortcuts. Every prob I had was that I didnt read instructions in close detail, and trying to use old hardware/parts. I tried to use a new 3/8 and the OEM 5/16 . It ran like poo when on the gas no matter what entry I pushed. Retrun line was too small: It said right in the manual: Use 3/8 line
For the FAST, my probs were JUST like yours: Exactly the same symptoms. It wasnt until I really looked inside the tank, canned it, and got another did everything clear up.