I would say that the three important considerations are the quality and the dimensional accuracy of the manifold casting so that it fits and port-matches well, the transition from ITBs to manifold if it's an adapted weber downdraft intake design (i.e. no ugly steps or sharp radius turns), and the quality of the ITBs and linkages such that low speed driveability is good. If those boxes are ticked OK, no reason why it wouldn't be excellent in operation.
Kaspa has experience with something similar on LS engines on his F5000 build.
From recent experience installing an ez efi on a stack injected ls motor for a customer, stay well away from fast EZ system.
The system constantly learns which is great but has draw backs too. Particularly on manual shift cars which confuses the ecu between gears.
The system i installed would not make fuel corrections despite getting correct inputs etc. It was wired correctly and everything functioned as it should but the ecu would not make any corrections.
Fast were contacted many times. They said it was electrical noise which it clearly was not. Sent video evidence and they went terribly quiet about the problems. Three months in they still wont respond both by phone and email. Ive lost count of how many times i have called them.
Check the fast forum for the typical and many problems people have with the product.
They have P..s poor customer back up and substandard product. Yep i got burnt and will not buy another fast product. Specially as i am out of pocket both time and $ on my customers car and they are so unwilling to help resolve the issue.
The holley system is much better or alternativly use a system where you have local back up and tuning availability close to you
About 2 years ago, someone on a forum posted some strong complaints about the ProComp system. Their main complaint was that it was a Chinese casting and that it wasn't accurate, the ports didn't match, and the machine work wasn't good. They had to do a lot of machine work on it before they could bolt it up.
The problem I had with it was that the injectors were on the outside pointing inward toward a wall on the intake. Thus, whatever fine atomization you had from the injector is spoiled when it hits a wall. I went with the Borla 8-stack system because their injectors were on the inside of the throttles pointing outward and directly down the intake. There are some other systems on the market that do the same.
Even with a good casting and precise machining as I see with the Borla, when you have a variety of blocks, different heads with possibly different port configurations, you might have to do some port matching and adjustments to get the intake manifold to match the head. I had to use double intake gaskets to raise the intake manifold up slightly to match the ports. I also had to do some hand cleanup on the manifold and head.
I went with the Performance Electronics ECU. I have had several years experience with them (actually since they started in business) and their customer support is great. I haven't started my engine yet, but I am in the process of wiring everything up and will give a follow-up report after I am running.
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