I disagree,
I bought one of the cheap chips off Ebay (like $40) and I noticed huge improvements especially over the 3k range. My friend has the exact same car with the Dinan Chip and I have noticed no difference between the two. Unless you have money to waste go with the Name brand one, but If you are a student like i am, get one off ebay.
No difference between two cars, both chipped means absolutely nothing at all.
I'll sell you my old
stock chips on ebay. Look under "BMW HOT CHIP +25bhp!! E30 325i, 325is, M3, 318is, 318i, 325e" I'll send you my old stock chip for your E30, but itwill be from my E34 525i with the M50. You won't know until you fire the car up and your computer is fried. OR I'll send you the one from my 318i cabrio, OR the one from my old 325e. Who knows, they all look the same. $40 turns into $500 for your new ECU, and then maybe if you have some cash left over, you can pay $200 for a proper chip.
Save yourself the worries and spend the money. $200 is squat.