GRB Misfire at idle and under transition/cruising

Hi, has anyone ever come across a GRB misfiring throughout transitions, idle and cruise? Misfire is very subtle but detectable. All basics have been checked without result. Car is running Deka 875cc injectors and am wondering now if either the supplied latency table is incorrect or the spray pattern of these injectors might cause an issue. Any pointers would be great. Thank you

Help me out here, what is a GRB? Is that some NZ/AUS thing? Do you have datalogs of the problem?

Sorry the Subaru WRX STI GRB (2008 on).

Are there any check engine lights? Is it giving you a misfire code? I'm assuming you haven't turned off the misfire monitor/trouble code.

Can we get a full list of modifications? Do you have any datalogs of the problem occurring?

No check engine light or codes, it is pretty subtle but still noticeable. List of modifications is 875cc Deka injectors, DW 300 fuel pump, TGV delete, upgraded turbo intake pipe, Garrett 3076R turbo, turbosmart waste gate, Process west intake kit and front mount intercooler, full 3 inch exhaust turbo back.

I've had similar problems with an SR20 that was fitted with a set of DeatschWerks side feed injectors. Wasted a bunch of time on it and ended up moving to a quality injector in a top feed kit which solved it. This issue was more prominent at idle than light load though. I also struggled with controlling the AFR at idle which was another hint to the injectors.

Is the issue solely at light load? If so then that would almost rule out the ignition system unless you've got something funky in the dwell table only at low rpm (assuming aftermarket ECU). It'd be a stretch I'd think but this could be related to a valve not seating properly. That of course would show up under compression and leak down tests though.

Thanks Andre, it happens at idle and between the 1500-3000rpm range. AFR's are perfect and stable and no misfire at all under higher loads or power runs.

Ignition system has been checked and all is in order, same with the engine. It is a freshly build engine and we have done a leak down test just to rule out any issues there. The ECU is stock, we have reflash tuned the car. Injectors are top feed, these are the ones in the car http://www.msel.co.nz/epages/motorsportelectronics.sf/en_NZ/?ObjectPath=/Shops/motorsportelectronics/Products/INJSD80S.

Anything else you could think of?