My car still has an issue on cold startups after being off for 5 hours or more.

I'll do my best to describe it.

She starts with no problem, sometimes may stutter and the revs go low and then rises and settles. I'll sit there and let her warm up for about a minute.
I put her in drive, she seems to take off ok but then the power drops away and for those seconds that it does, accelerator movement does nothing, just feels like it's flooding, and when I let it sort itself out the power comes on but much harder as if it's suddenly burning the extra fuel thats been dumped into the cylinders, kinda like spooling up and I have to take my foot off the pedal until it settles again, about 3 or 4 seconds.

The other day I tried something different, when she did it again, I kept the accelerator pedal still, not letting it out or pressing furthur, just kept my foot steady, and I could feel the engine power surging like a sine wave, the power went up a bit and went low, back and low, up and low.

Can this be a blocked injector causing a cylinder to drop out, or is it most likely ECU driver issues or actual fuel pump. Fuel pump is quiet?
There is an issue where the revs drop almost 200rpm when the air-con goes on, not diagnosed but probably the ECU.

The leads are fairly new, plugs are new, fuel filter is pretty new?

Other things to consider are a recently replaced intake gasket, where I tried to block 3 holes with gasket goo but a bit may have been sucked in as it wouldn't dry. But the gasket replaced now.

What do you guys think, I'm thinking about putting an XR6 ECU in my stock I6 Fairmont but am affraid of wasting money on dud fixes.

Cheers.