The topic of reducing intake air/fuel temperatures has been well documented, both for performance gains and preventing vapor lock. If you need justification, just think about the cooling fans Fiat added to the carb and FI intakes. And there are many great examples of phenolic spacer/insulators added under X1/9 carbs (for stock and performance setups). But in the same way that a insulator spacer can be added under a carburetor to reduce the amount of heat transmitted to it, the fuel injection intake manifold itself can be insulated from the head with a similar spacer. This seems to be gaining popularity with VW's, Miata's, Japanese cars, and many others. Several companies are making custom cut phenolic insulators (typically around a quarter inch thick) to install inbetween the head and the intake manifold. Here is a little article on it: http://www.autospeed.com/cms/article.html?&title=Cool-Stuff-Manifold-Insulators&A=110474 And here are some examples: I'm looking at making phenolic spacers for the X1/9 fuel injection manifold. But there are at least three possible approaches (that I can think of) with it's counter-flow head design: 1) Due to the shared gaskets and mounting studs for the intake and exhaust manifolds, the insulator could go between both manifolds and basically duplicate the shape of the manifolds' gaskets. This might(?) provide an additional benefit by separating the exhaust manifold from the hot head, therefore reducing the heat that rises up from the exhaust manifold to the intake plenum? Not sure exactly what the outcome would be. But it certainly simplifies the mounting arrangement because both manifolds will be raised the same distance from the head. So with longer mounting studs everything will install normally (just need two sets of gaskets). However I'm not certain how the phenolic material will hold up under a exhaust manifold. I did some lab testing of the material and found it will burn (as in actually catch fire) if it gets hots enough. But that was at an extremely high temp (I did not record the actual temperature when this happens, I'd estimate it was over 2000* F). The testing did show it to be strong enough (physically and chemically) to stand up to the weight and load of a exhaust manifold sitting on it. 2) The insulator could be installed under just the intake manifold but not the exhaust manifold. This puts the two manifolds at different mounting heights so some metal spacers would be needed over the exhaust manifold's shared mounting tabs (to bring them up to the same height as the intake manifold). That is common for installing tubular headers, so easy to do. It will avoid any issues with the higher heat levels of the exhaust on the phenolic material. And the entire intake manifold and injector bodies will be insulated from the head. A extra set of gaskets will need to be cut and the intake portion used on the spacer. One potential issue might be with the different mounting heights for the manifolds; it may make getting a good seal for them more difficult. 3) Instead of installing the insulator at the head, it can be placed between the lower runners and the upper plenum halves of the intake manifold. This would be easier as far as mounting the manifolds and spacers go. And might be less prone to leaks. Naturally the biggest drawback is it only insulates the upper half of the intake. So the runners and injectors will still be hot, reducing the benefit. Another lesser issue is the mounts for the injector rails will need to be adjusted (where they attach to the plenum) to account for the added space in the middle of things. This approach has being taken for some other engines due to the complexity of their manifold: All of these approaches will require an adjustment to the throttle linkage due to the manifold being slightly further away. But that is easy to correct. Things like wire harnesses and fuel lines will flex to accommodate it. Until it is mocked up I won't know if other adaptations are necessary. I think I'm leaning toward the second approach (between the head and intake manifold only). Any ideas on that? I won't address the overall trade-off of 'benefit vs effort', that is up to each person. And as to comments like "it doesn't need it", or "why modify the stock system", or "you are over thinking it", or any other judgemental remarks - . But I do appreciate constructive comments on the project.