Since no one has answered the materials question I'll share a little of what I know.

Plastic is used for two benificial reasons, the first is that in high volume the manifolds can be made real cheap and secondly they are poor conductors of heat and keep the heat of the enigine from heating up the intake air. (Good for TPI) The downside is that it's harder to mod and must be high volume.

Aluminium is lighter and cheaper than cast iron for manufacture, fabricated manifolds are too expensive for production cars. The downside of aluminium for performance is that it conducts heat from the head where it flanges all the way up the intake runners heating the intake air.

Mild steel is much less conductive than aluminium and will heat up the air less but cast steel is expensive and as I already said fabricating manifolds is too expensive for production cars.

Even better is stainless steel as it's even less conductive than mild steel and has a high thermal capacitance which will result in the heat not travelling as far up the runners.

Thinner pipe/ tube walls will reduce the heat conducted from the head up the manifold as will insulative plates and washers on the nuts. On the other hand cold air can increase exhaust emissions and fuel consumption but you're after power right?

Insulating the outside of the intake runners will only help if there is heat radiated from the exhaust or if the intake is cooler than the air in the engine bay and if it's aluminium the intake is likely to be quite a bit warmer than the surrounding air, in which case insulating the outside would only increase air heating inside the intake.

I believe some old v8's had cast iron intake manifolds, there may be others, maybe a ford motor? I think I've seen an old tractor with a cast iron intake manifold to.

Ultimately it depends on what you want to achieve.

I have found Steel easy to work with and after thermal coating just as good.

The import (Black tappet cover) motors apparently run 45mm and South African motors run 43mm. This is what I read on VW site.

The Toyota motor is 1600cc but remember it has more modern valve train and also revs to 8500rpm. The VW cylinder heads in my view are still dinosaur designs.
As stated previously, go quad throttles. How much will it cost to choke the Toyota throttles? Is it as simple as just fitting a sleeve? I would have thought that there is more to it.

Racetech just run 4 throttles and choke them till you are happy. I mean a rsi is a 1.6l i just think the golf guys dont know what they are up to.

my veiw on dual vs quad would be go for quads. if you run quads you're likley to encounter less corruption of you vaccuum signal to the other cylinders though exhuast gas reversion from valve overlap if you run a big nasty cam. (and you should too!) This is why you'll get a happier idle with say twin sidedraft delortos/webbers than with a single carb.

Thanks force.

Anybody with views on the dual or quad throttle bodies and the Alu vs. Mild Steel Intake Manifold.

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basically, you just modify your distributer to hold a cam angle sensor from another engine. (Say a CA18DE/DET etc) Then connect the CAS shaft to the dizzy shaft. You also need to dismantle the CAS and invert the disc inside it as the CAS and the dizzy rotate in oppposite directions. Then the CAS can tell your ECU both the speed of the engine, and the location of the crankshaft. Then run one coil per plug and let your ECU do the rest.
I fully intend to to this to an A14 I have in the shed, and use full CA18DE/DET management, remapped by a mates nistune tool.

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your talking about inlet manifolds right....dont think ive ever seen a cast iron one. only alloy or plastic.

1200gx so the rxi throttles is 45mm and the rsi ones is 43mm. I'm looking at the 43mm throttles.

I'll choke them to what is needed, a lathe and a piece of Alu will sort that, just need to get hold of someone that is running 4 throttles and the sizes they are using.

Personally I can't see the reason besides ALu is cooler and will stay cooler than MS, but a little powder coating will fix this, even heat wrap afterward. Almost all OEM manifolds is cast iron, only custom made stuff is alu.

1. RXI throttles I think are too big. Look at motorcycle
throttles of size 36 to 38mm. The SU's are 38's.
2. Use aluminium. I have not seen one intake made of
normal metal and there must be a very good reason they
are all using aluminum.
3. Talk to kululadotgroen on the site. He explained in
detail to me how the different trigger mechanisms work
.He is also as I understand in the process to go crank
angle sensor.
4. Go 4 throttles not 2. It will give you better responce
and I think more power.

This info is not from personal experience but all the stuff I have read on the VW Forum. Those guys have tried some nice combination of stuff. Apparently the RXi throttles are too big for even the 2 liter 16 valve VW motors. They get better power from 40's or the RSi 43mm.
Your motor is 1400cc. I think it will perform better with a slightly smaller throttle. Check the bike stuff out to get a decent size.Let me also know what you come up with. I want to go bike throttles in the future but here in Bloem there are nothing.Will have to look in Jo'burg or in Cape where bike scrapyards are plenty full and hopefully at the right price.