I've read around abit on the forum and came to the conclusion (which I already knew really) that there isn't really any parts for the Z5. I've seen a few things here and there that people say you would need to alter slightly. I was wondering if there are any parts from other engines that would work on the Z5 to increase power? I was also looking at megasquirt ECUs but I don't know what there is to be gained out of one after all the supporting mods.

There's not really anything you can do by simply bolting on parts - the aftermarket support just isn't there, and the engine itself is pretty unique in its parts.

Aftermarket ECU won't net much, maybe a smidge, but unless you're going forced induction I wouldn't bother, personally.

You could port and polish the intake manifold, maybe some headwork, and maybe see a couple of extra BHP but it won't be particularly noticable on the road.

I built a mega squirt ECU for the Z5 many years ago! It cost a ridiculous amount of money but I was looking to add a supercharger so would of needed it.

As Hughie says, if you're keeping your engine NA then don't bother with an ECU. Maybe get the head skimmed, port and polish the intake, stainless exhaust manifold, decent intake with CAI....do all this and you might see 105bhp at an absolute push! It would be a lot of money for very little gains unfortunately.

Hmm yea, alot of money for nothing. So pretty much will just have to leave everything as is when it comes to the power of the car. Only thing I can do really is good tyres and lowering springs pretty much.

If you want to race with it, well that engine isn't the propper base you should throw your money at.
Maybe 1.8 to 1.8T will give you some good gains or V6 to V6T, but MPG will be alot different.With Horsepower comes bigger costs.

Yea wasn't looking to race with the 1.5, was just seeing if I can make it more fun on the road. Which seems I will have to do that with suspension, tyres, and stuff to make the car all around nicer inside and (to a lesser extent) out.

Give it some more base timing. That and proper maintenance. Depending on the fuel available, you can set the base ignition timing a lot earlier which I found to wake up the B6 and BP engines quite a bit. Should be similar with the Z5 but please keep out an ear for engine knock.

Just to add my little bit: I think the 1.5 is a well-balanced engine as it is. Make sure it's working as it's supposed to be (i.e. all the service items replaced as they should be).

It tootles around very well at low revs, then if you need a squirt you accelerate and it wakes up nicely at 3,000 revs and goes very well for a normal non-turbo engine.

I've never tried to modify the engine, so can't speak from experience on that, but I like it the way it is. If you want more speed then you buy the 1.8 or the 2.0.

Yea I can't really do much. In my country only the 1.5 was ever sold
As you said just have to make sure it's serviced perfectly and all that.
If I want proper power I'll just have to save up for another car in the future

You could export a 1.8 from the UK to your country!

That's been an idea lingering in my head for a while
Someday might actually do it but tax might screw me over if it's even legal to have an engine swapped vehicle on the road.

But someday I'll do it. I would do it with a v6 if parts were even available but they are just to scarce and expensive.