Have a EG8 civic with a JDM D15B which until recently was failing to start.

I borrowed my mates coil from his EK as (his EK is stuffing out with idle problems stalling (automatic transmission)) and my civic is working again but soon as you give it around 3-4k rpms it seems to go in some sort of limp mode and drops rpms close to 0.

It feels like it has the problem my mates EK has, it's close to stalling and hits almost 0 on the rpm gauge.

Tried my mates rotor, dizzy cap and the cap covering the igniter and coil but no luck.

Any ideas?

Latest update:
Cleaned out the IACV and Throttlebody, reset the ecu and the problem seems to be worse.

It started fine the first time, idles started dropping to 0 and actually stalling where as before it used to drop but not stall.
Having to give it throttle while cranking to get it to start now. It'll probably start first pop when its cold again, but soon as it warms up it needs throttle while cranking to start.