Check all over for a vacum leaks. That's what it sounds like.
Do you have the plug wires on in the right order?
On the throttle bodies, are they seated with no gaps between them and the head? Make sure nothing is pinched.
Do the plugs look good?
Did you test the compression? If so, is all the cylinder PSI almost even?
Are all your lines and connectors hooked up in the right order?
How about the vacumm lines on the throttlebodies under the airbox? The ports that you hook a vacumm gauge up to, to sync the throttle blades. Make sure they're plugged or lined the way they need to be. Jinkster's "How to sync your throttle blades" how-to has a great description and pics on how these lines are supposed to run.
Maybe they're is still some gunk in the fuel lines. Remove it, use some carb cleaner and a air blower to clean it out. A few pieces of dirt in there can mess with the fuel system.
Also, check the fuel delivery throughout the fuel pump.
Is any of your ECU, throttle bodies or wiring of different years? An earlier ECU isn't friendly with any late model hardware. Make sure it's matched to the right year groups.
Was there ever any rags stuffed into the throttle bodies to keep dirt out of them that might of been sucked into the motor?(I've seen this first hand on a few cars)
I'd start with one area and work my way over everything that can interfere with the Busa's engine operation. Eliminate every possibility. Whatever is left over, no matter how remote or improbable has got to be the problem.
Pac, you'll beat this.
Whew...this is gonna be a good one. Dayum.
haven't checked for vac leaks...don't exactly know how. Good place to start, though.
Plug wires in right order.
Nothin pinched on the TB's...they look to be seated properly.
Plugs are new...just replaced. Guess I'll pull them out and look again.
Haven't checked for compression. How would I do that? I'm hoping I don't hafta tear into the engine. That's a whole lotta work.
Lines and connectors are hooked up in the right order, I believe. Vac lines under the TB's and airbox appear to be ok. I hope I don't hafta synch the TBs...that looked real complicated.
Don't think there's any gunk in the fuel lines...they seemed to be clear. I'll check 'em again, I guess. Sigh.
Fuel delivery throughout the pump should be fine. At least, I think so. I hear it suckin gas from the tank, so that's a good thing. Oh gawd...please tell me I don't hafta take it apart again and remove the all the insides.
ECU is from a 99, as is the wiring harness. All matchin there.
No rags inside the TB's. Did my best to make sure that nothin got into the TB's. I knwo that's really bad juju for the engine.
Sigh...starting over again. Yay. Damnit....
Thanks, man...I appreciate the encouragement. I'm so tired of all of this, though. Fudge...