1995 3.4L Pontiac Firebird Crank No Start

Hi all, I’m completely stumped trying to get this car to start, hoping someone can think of something I might be missing.

It’s a 1995 Pontiac Firebird with a 3.4l and 220k miles. It was parked 4 years ago with a blown head gasket. It did run before it was parked.

Replaced fuel pump yesterday (it died while sitting there) and it wouldn’t start, just a short cough/sputter every now and then on a couple cylinders. Sounded like a heartbeat. Continued with the head gasket job anyway.

Did/replaced the following:
– Head gaskets
– Exhaust manifold gasket
– Intake manifold gasket
– Intake plenum gasket
– Spark plugs, gap checked
– Plug wires
– Fuel filter
– Valve cover gaskets
– Water pump
– Thermostat
– Oil filter
– Changed oil (was absolutely full of coolant)
– Plugged all vacuum lines (waiting for vacuum harness)
– Drained fuel tank and added a few gallons

Set valve lash twice following service manual. Though I have read this is difficult to get right and I’m not sure how to know it’s correct for sure.

Fuel pressure sits at 41psi, within spec. Spark verified on each cylinder. Plug gap was checked. Compression test gave the following:

1 = 180psi
2 = 150psi
3 = 210psi
4 = 180psi
5 = 120psi
6 = 210psi

Minimum compression according to manual is 100psi.

Fuel pressure regulator tested good.

Even after all that, it still does not start. It DOES start for a moment when using starting fluid. While cranking it has the same exact rhythm as it did after I replaced the fuel pump – a sort of heartbeat rhythm with only one or two cylinders.

So I’m stumped at the moment while I wait on the new vacuum harness. In the meantime I’m hoping someone may think of something I haven’t.

Anyone have any ideas?