EFI Mapping Questions....

[avos at cochlear.com.au]

     I have a question regarding the altering of EFI parameters from a 
     factory Management computer. My car is a Subaru and I brought it with 
     an after-market EFI chip installed by the previous owner. The chip was 
     designed in Australia. I had a bit of a think about how to design such 
     a chip, and came to the conclusion that modication of my chip would 
     only be feasible for a small company if the chip was a standard PROM 
     and the people who developed my chip simply down-loaded the data from 
     the factory chip, worked out how the data effected the paramters of 
     the management computer, and modified the data for new parameters, and 
     then burnt a new compatible PROM with the data. Is this a way that 
     aftermarket chips can be made?
     
     If this is the case and the aftermarket chip is simply a PROM, than I 
     should be able to download the data from this aftermarket chip into a 
     file and edit it, and burn a new chip. The main question I have is how 
     do I find information on the PROM memory map? Is it likely that the 
     makers of my aftermarket chip worked out how it worked by trial and 
     error, or would they have had a manual which explained the memory map 
     of the chip. Is it common for car manufacturers to give such 
     information to the general public. If so where would I be able to get 
     it for a Subaru Liberty RS Turbo.
     
     I have recently found out that another maker o EFI chips in Australia 
     is making a chip which alters the factory boost level in the chip (The 
     boost level on my car is controlled by the computer). I am currently 
     making my own boost controller, but I can't help but wonder about the 
     option of modifying my boost level in a reliable electronic method by 
     such a simple thing as changing the PROM. This would be far cheaper 
     than any other method I know of (including the standard boost bleed 
     mechanical method), but would retain reliable/accurate boost levels 
     achieved by after-market electronic boost controllers as it is 
     essentially an electrinic boost controller intergrated in the factory 
     management computer.
     
     I am not interested in changing fueling parameter currently as I don't 
     know enough to do this, and could easily damage my engine. Currently I 
     am only interested in altering the Boost level.
     
     Before anyone asks, I don't know what type of computer Subaru uses, 
     but If anyone would car to tell me I would like to know......
     
     Thanks in advance for any information on this subject. I would have to 
     assume that some people on this list have modified factory map 
     settings before...
     
     Adrian