3.4 rebuild running lean

[STU911Targa]

Hi All from Australia,
Background: Competition Tarmac rally car '87 911 Australian edition.
Have retired from competition and returning to a road car.
Engine was: JE 3.4 pistons, SSI, Doughterty cams, PMO carbs, Dyno 195Kw/260HP
Engine now: JE 3.4 pistons, SSI, original EFI, ECU (not chipped) compression 190-200psi running 98 octane.
Problem: Engine starts OK, but within about 30secs starts to run lean on gas analyser and stays lean regardless of revs, so I switch it off.
Have swapped out distributor, ECU, DME, sensors, fuel pressure OK, but still runs lean.

Do you think the extra 200cc is just demanding more fuel?

Have considered a Steve W chip, but wonder what yo all think.

Thanks Stewart