Actually, factually incorrect. M50 and M52 motors both share the same common identification codes, being 206S and 256S, therefore are the same blocks. Argue this all you want, I have the paperwork in front of me to prove those ID codes, it's all readily available information.
The M50B20 and B25 both have a larger intake cam, however, as the TA's car is a 1995, it will most likely have an M50B25TU motor, the first of the Vanos ones, which has basically the same cams as the M52B28. So wrong again on that fact in relation to the TA's car.
No arguments at all regarding the exhaust, it can use a lot of improvement over factory regardless of what engine you have. However, keep in mind that runner lengths, shape and size, as well as design, can be used to change the engine's dynamics.
The M52B28 has 5mm more stroke, hence why it has more torque. I don't think there's any reason I need to explain why 5mm difference in crank stroke makes a difference to both torque and ho, do I? So the question becomes, if the M52 is so much better designed, why then do you get a good result from throwing the M50 manifold onto it? Why does that make the air velocity "too slow" for the M50?
In theory, the M52 is an overly square design (1:1) when you look at bore and stroke measurements, therefore it should not like high revs, will rev slower but will produce a higher torque figure for the available hp. The M50, on the other hand, is a 1.77:1 rod/stroke ratio, which means it will be happier revving harder, however will produce less torque. Still produces almost the same hp as the M52 though.
“Minor mods” to the M52 usually start with putting the M50 manifold on, to increase air flow into the motor. After that is exhaust, tuning, cold air intake etc. So if the M50 manifold is such a poor design, with runners that are too large, why is it so effective on the M52? Can’t be the camshaft lift and duration when compared to the M50, only the intake cam is larger. And that’s only with the non Vanos motors.
I do agree a properly designed set of headers will do a lot of good, yes equal length (if possible) is definitely the way to go. There’s a lot more factors that come into it, depending on what you want to achieve, such as primary diameters, overlap with exhaust ports, etc. etc.
Going back to what the TA originally asked, he wants a “lil bit more power” and is looking at a chip, I am guessing it’s because he doesn’t want to spend a s**tload in swapping motors, certs, fancy custom made exhausts, cam grinding, and so on…… all of which everyone else is telling him to do. Chips bought ex USA from Turners are around $350 (and I’m positive there are other well known tuners that you could get cheaper chips from). I want to know where I can buy an M52B28 for $700 (the price of two chips as you stated) and get it installed in a car without any extra costs, no certs, nothing.
On and FYI, Turners chip? 20hp and 13Nm torque increase….. a bigger increase than you predicted after spending $600 or more on an custom exhaust.
The chip is still the better “bang for buck” mod.