CM871 Idle Fluctuation

[multitask]

Hi everyone,

Have an 871 and every 3-5 seconds the rev will drop alittle and make a huffing sound.

This is what I've done so far:
Egr tune up
Changed IMAP and exhaust back pressure sensor
Cleaned all piping using carb cleaner
Cleaned egr temp sensor and delta P using carb cleaner (hope that wasn't a bad idea using the spray?)

Yesterday I removed the egr pipe that's between the egr valve and Venturi but with the sensor still connected I started the truck and she idled perfectly!!!! (All sensors connected and no faults active).

Could it be the egr or delta p sensor causing the problem? Is the egr valve meant to be closed during idle? Was getting exhaust gases coming out.

I've also tried running the truck with the egr sensor unplugged and she runs like a dream, but Rawze did tell me once that will derate the engine etc

What's you're recommendation gents?

Thanks