Power Restriction / Idling Issues

[Dpilton]

Hi All, First post here and hoping you lovely people will be able to help me or help point in the right direction.

I own a Mk2 Scirocco that has been modified by a previous owner. In terms of modifications, the information I have is very limited as the owner that modified it was a few ago and therefore probably lost through ownership passing it on, however; in terms of engine it has an Audi 80 2.0e litre bubble block, head from a mk2 golf GTI 8v with Ashley four branch manifold. It's had a digifant injection system fitted. Still has distributor and coil, inevitably a lot of wiring has been modified to fit this. Also got the air flow meter which has been set to a happy medium to pass emissions but not running too lean. Hopefully this will give enough baseline to go...

I'm experiencing major issues with power loss (almost like a limp home mode which I suspect this is too retro to have) and a spurious idle. I'm convinced the two are linked but can't be sure. Links of the two issues are shared below although appreciate the power loss one isn't the best so apologies:
Power Issue https://www.youtube.com/shorts/P2D1-scWRtQ
Idling Issue https://www.youtube.com/shorts/32mgaltf9ec

• The idling issue seems to get worse when the car gets up to temperature after 5 mins of driving, it was doing it sporadically but seems to be a more common issue now. When slowing for a junction and dipping the clutch, its enough for the car to stall as well.

• In terms of the power issue, this seems to occur after the idling occurs but isn't limited to this, it can manifest itself in a complete power reduction, with foot to the floor in second the car just sits at 20mph/2k revs with no power and judders until suddenly the issue disappears and it picks up. This can also manifest at any speed, gear or rev range. It also come in the form of whilst driving up through the gears a massive blip (almost like a misfire) before cutting back in

Obviously appreciate this problem isn't necessary limited to the engine and could be fuel, electrical or control. Also appreciate the setup isn't exactly common but I'm at a loss really of where to start and would appreciate some ideas or if anyone has had anything similar before I start going off down the various avenues of investigation.

[james butler]

first thing that springs to mind is massive air leak somewhere

[Dpilton]

Hi James, had a good look for air leaks to no avail, including spraying everything to listen for a change. Nothing is consistent.

What I have found from general investigation so far is the following:

• Digifant box appears to have been installed in a bit of a hashjob without being rude, the actual box isn't mounted and just chucked in the wiper bay, possible vibrations wouldn't help. So secured this

• Ignition leads have been reterminated to the coil, however the female part of the plug is missing and a crimp with exposed conductor free to potentially short out (feed to the coil) to the body

• Distributor cap when disconnected arcs from the coil to the body of the cap, the distributor is clean and only covered approx 1000 miles since fitted by previous owner

• uprated fuel pump in engine bay, wired directly to fusebox with ignition turn on

• The lift pump in the tank appears to have a very low flow rate, not sure if this is correct as I assume its meant to have some . However, in this system the OEM lift pump feeds a filter on the underbody, this then feeds to a Sydac GSL392 Fuel pump in the engine bay, this goes to the injectors and returns to the tank via what I assume to be a regulator. All in 5/16" hosing

I've read mr.brown's excellent post in this section about carb to injection conversion, it seems that the fuel system hasn't really been thought about in this instance and certainly doesn't match what I actually have fitted, is the above system missing some sort of accumulator/swirl pot to allow for surges on hills/cornering or is this a credible system with the aftermarket Sydac/Walbro uprated fuel pump?
I think unfortunately I've got several issues all combining, however I think fuel is probably a good place to start if anyone can shed any advice on the matter?