I bought a 2000 civic si(canadian si, american ex) and it has a d15b in it, stock they have a d16y8. The motor runs okay but it cuts out at 5k rpms and obviously that's not good. It has a p2p ecu in it which is the right ecu for the car but wrong for the engine. My question is what should I do, get a p08 or keep the p2p or get a different ecu and have it chipped with a p08 basemap? Sorry if this has been posted before, I've been looking for days and couldn't find anything on it.

 

Get a different engine.

 

So you think I should just get rid of the d15b and put a y8 back in it?

 

Yes

 

while the Y8 is a more HP/torque engine, it's not exactly the cheapest solution.
the easiest/cheapest would be to get the right ECU for the engine.

first step there is to figure out which D15B you have. (there are many)
start with the head code. Just above the exhaust manifold. (p08, P06, P07, P... you get the point)
once to figure out what engine you have, get the right version of ECU to control that engine.

the other part of the equation, do you need OBD2 scan tool compatibility. (ie for emissions testing)
Only USDM ECUs are emissions compatible, many flavors of ECUs that control the D15b are not available in the US.... even less are OBD2b (which your car/harness is)