During takeoff climb out I experience a hiccup in the engine. If I keep full power in it get worse by more missing.

Pre-takeoff check is perfect--both "mags" same drop, ~70 RPM; fuel pressure 6.3 psi

On takeoff with full power fuel pressure (initially 6.3) and fuel flow (initially ~5.3 gph -- fuel flow not precisely calibrated but close) gradually declines. Hiccup consistently first occurs when fuel flow declines to 3.4, usually on crosswind but sometimes early downwind.

Facet pump will return fuel flow & pressure momentarily, eliminating hiccups. Reducing power also restores flow & pressure.

Upon landing and doing repeat run-up all indicators are again normal. Repeat take off again results in hiccups but more of them.

Tried a flight yesterday. Climb out was good, fuel flow & fuel pressure good until about 2700 AGL/3500 MSL then had hiccup. Reduced power and no hiccup. Did slow flight for 15 min and then experienced hiccup again.

Fine fuel filter is clean. Cleaned second time--no change. Fuel cap vents clear. No kinks in fuel lines. Rubber fuel lines replaced 18 mos ago.

Fuel plumbing (in order): Wing tanks with coarse filter, header tank, fuel valve, fine fuel filter, Facet pump, engine fuel pump (newer style pump), "T" for fuel return line (with fuel pressure sensor then carb jet restrictor then feeding into L wing tank), fuel flow monitor (Red Cube), "T" for split to carbs.

700+ hrs on engine. Recent problem occurring. Problem began after condition inspection. Very smooth except for hiccups.
Carbs rebuilt by Lockwood 160 hrs ago. New type floats.
New plugs at condition inspection. New plugs again after experiencing problem. No change.
Replaced broken module bracket (pn 851-480) and installed fuel pressure sensor during condition inspection.

Related or not??? About two months ago engine would not fire at all with several attempts. Normally quick starting. Next day I tried again and it started without hesitation, without any changes/corrective action.

My plan is to check electronic modules by trying to start engine individually with each module.

Thanks in advance for any suggestions/observations?