E 4 and E 29 are parts located inside the cockpit and I think they are some kind of throttle control or something like that.
You need do color those parts and thats it
Watch out for parts E 13 and E 5 they can't stand on the place they should cause the cockpit floor can't fit then so you need to test fit before you glue your parts.
I think you can see that on the photos on my I-16 topic
Hope I have been of some assistance