I have spent weeks discovering a huge memory leak in magento. It duplicates an array of products over and over. So for example you tried to import 1000 products you would have an array containing 1000 products 1000 times. It eats up memory but also a lot of cpu parsing the info. I have cut down my script import time dramatically. There are other memory leaks that deal with object clean up that haven’t been able to pin-point but have a method to fix that too. The fix is only 1 line of code. If you are willing to compensate me I will give you the fix. I usually would just post it but I really had to spend a lot of time and compile php into debug mode and run it thru valgrind and then use a php debugger.
If you import more than 100 products this fix really helps and it speeds up regular magento operation as well. I contacted magento about this and they did not reply.
message me or email if interested
I also sell a couple of modules at http://ewtechnologies.com/store/magento