Inlet and Exhaust Systems

Inlet options:

• KR (Golf Mk2 GTI) Inlet Manifold - T/B Exits at Offside rear of engine bay.
• 9A (Passat, Corrado) Inlet Manifold - T/B Exits at Offside rear of engine bay.
• Scirocco 16V Inlet Manifold T/B Exits at Nearside rear of engine bay, in similar location to std mk1 GTI.

As a side note, there are two specs of the 16V manifolds. Ie with different diameter runners. The larger ones are rarer, have a look through the CGTI thread on this, whether or not there's a benefit to the different specs has been debated.

Another point is you cannot use the Audi inlets, the T/B exit is in the wrong place.

Exhaust options:

There are several issues to think about before exhaust manifold fitting and choice.

• Main Exhaust System. Use whatever main exhaust system you wish for the conversion. If using an aftermarket conversion manifold ask the manufacturer about fitting to existing systems. For exactly this reason some are supplied too long to allow adapting to fit whatever exhaust system you have. Some manufacturers offer matching exhaust systems to link up the conversion manifold, and some may just fit straight onto a standard exhaust.
• Heat protection: the steering rack gaiter is very close to the manifold so should be protected, either by heat wrapping manifold/down pipe, or protecting gaiter and vulnerable wiring etc in the vicinity. Various heat protection products available.
• Clearance of ARB: If a front ARB is fitted the manifold must clear it. Trial fit manifold to check it clears as some lower quality manifolds can have variation in manufacturing meaning they knock on ARB or floor pan.
• Flexi-joint: It is important to consider that if fitting a solid four branch conversion manifold with no flexi-joint, it can crack under stress from engine movement. Standard exhaust systems have a flexi-joint between manifold and downpipe to prevent this. Some aftermarket manifolds have them fitted already, however if not, preferably fit one as close to the engine as possible to absorb the engine movement.
• Engine choice. If using an ABF, the taller block 16V, the Supersprint/Raceland manifolds offer vertical adjustability so are 'more' suitable. Remember aftermarket manifolds are not always perfect, and be aware you may have clearance issues with the top section.

Common Exhaust Manifold options:

• Scirocco 16V Manifold/Downpipe. Either OEM or Aftermarket (available in the US).
• Custom Mk2 Golf 16V manifold and Mk1 GTI down pipes - Cut and welded as required.
• Ashley: Steel 4 Branch Mk1 16V conversion manifold. Comes in two parts, a 4-1 main manifold and a kinked lower linking section to connect to your system, exiting at 2.25" diameter. They join just before the ARB. Available new approx £190 from rally parts stockists.
• Storm Developments / DubPower: Stainless Steel 4 Branch mk1 16V Conversion manifold. Comes in two parts, essentially the same design as the Ashley 4-1 manifold, however they have added a flexi joint into the lower section, negating the need to add one yourself. Build standard reputedly higher than the Ashley.
• Supersprint Stainless Steel 4 branch Mk1 16v conversion manifold. 4-2 and 2-1 sections. They join higher up in the manifold, allowing some flex and vertical adjustability (For tall block engines, ABF etc). These tend to be regarded as the 'best' option however are the most expensive!
• Raceland Stainless Steel 4 branch Mk1 16v conversion manifold. Have only seen these on ebay, they appear to be cheaper versions/copies of the Supersprint 4 branch.
• G-Werks Conversion Manifold. No details known.
• Maybe others now?

My experience: 9A with Ashley 4-1, I heat wrapped the upper manifold section and had the lower part adjusted with an additional bend and a 2.25" flexi joint, made to give plenty of clearance over the ARB and link up with existing 2.25" system.