if you're still looking for the parts, these are some of my favourite websites http://www.japaneseimportspares.com.au/home/ http://www.nengun.com/
also some of the ebay sellers are really good for oem parts, i don't get performance parts off there though and i did a bit of looking on nengun and found a few of the things you were looking for http://www.nengun.com/nissan/skyline-er34-first-term-genuine-air-filter-445750 http://www.nengun.com/nissan/skyline-er34-genuine-intercooler-439547