I'm a fan of DIY EFI. I built my system from junkyard parts but I modified the ECM with a circuit board from http://www.dynamicefi.com/
. Basically this board allows for a great amount of feedback when chip tuning. The board I used was called the EBL Classic. A new board is now available which is called the EBL Flash. The EBL Flash board negates the need for buying an EPROM Programmer since the onboard flash memory is used instead of an EPROM.