Cheap thing you can check yourself
Hi, I found my problem that had the same sort of behavior.
Have a look on the inside of the mudguard beside the battery.
Autos have 3 relays, and I think that manuals would have one.
One of them is a metal one that looks a bit like the one in the photo.
The inside is shown in the other photo.
This relay should never operate, as it is there to protect the electronics is someone connects the battery up the wrong way.
It supplies power to all of the injectors, (through all that green and brown crap you can see in mine).
I replaced mine with a short piece of heavy wire with a male spade terminal on each end. This is stuck in the relay socket to join the orange/black wire to the red wire.
My car is running the best it has since I got it :w00t: :thumbsup: :yeah:
Check yours and let us know what you find.