I have recently bought a mk6 fiesta zetec 1.4 petrol and I am in the process of tuning it because I like a challenge (praying I can break 125-150hp out of it) and as I am uprating the engine power and torque I thought it would be wise to also upgrade the clutch and fuel injectors and pump, I am just wondering if anyone here knows if the ST150 transmission components are compatible with the zetec. It would save me a lot of time and money.

just buy a st as there only a few grand now, when they was new yeh go for it but cant see the point trying to get 10 20bhp out of a 1.4, will you be changing the cams on the engine ?

I wouldn't have thought fuel or the torque capacity of the clutch will be a limiting factor.
You'll be doing extremely well to get 150bhp from a naturally aspirated 1.4!

As for the gearbox I believe they are all ib5 with different ratios. The ST has a stronger 1st gear and a different final drive than the others. They might be compatible but I'm really not sure

The ST is the only Fiesta that used the Mazda L/Duratec engine that came in 1.8/2.0/2.3 variants.