04 GTO Losing Power at 6000 RPM under load

[mrGame]

Hey everyone! I have a 2004 Pontiac GTO that we just swapped a 417 11.5:1 LS3 into. It's got Dart Pro 1 heads, a cam motion custom cam, Holley 2 piece single plane intake with an Accufab 4150 intake. It made 485 on the dyno cutting it off at 6000 RPM, because after that it starts to break up and pop and doesn't make any more power. The dyno graph actually looks very jagged after that, before it is a nice steady climb. I've checked grounds, fuel pressure is good, valve springs are good, oil pressure is good, and the crank reluctor is straight (I looked at it and rotated the engine. It's also welded to the crank). Plugs are NGK TR6 gapped .024 and I have brand new AC Delco wires that don't have any damage to them. I tested it on the track and it revs beautifully in the burnout to 6500 RPM, and does it so quickly it triggered the electric shifter (it's a powerglide). Then when I footbrake launched around 2500 RPM it laid over again. I've been working closely with my tuner and we're both kind of at our wits end with this thing. Has anyone else seen this?

Edit: This is with FAST 60 lb injectors, a Deatchwerks high output fuel pump and on 110 octane leaded gas

[FASSTRUK]

Tune, and log of when it happens?

[kevin87turbot]

Very likely a crank sensor issue. I've seen it before. Make sure you have an AC Delco sensor.

[mrGame]

Very likely a crank sensor issue. I've seen it before. Make sure you have an AC Delco sensor.

So I replaced the crank and cam sensor and my coil packs (cyl 7 was weak on a voltage test). Car ran perfectly last night. Thanks all!