BMW Repair: e30 leaking heanders, air flow meter, stop screw

Question
just install supersprint headers, muffler,center res, Schrick 288 cam w/ springs. I have re-justed the stop screw . car will idle then cut off , even if I drive it after 5 or more min it will lose power. maybe  get to rich. I do have a leak at one of the headers at the down pipe. Just trying to catch the shop and have it fixed  . do you think this could cause my problem . everything is new . 02,cap,rota button, wires,plugs,coil 45volt, fresh head,also hard to start have to give it gas . thanks  

Answer
William,
 Sounds like you should have a pretty hot little engine there.  Unfortunately if you know about modifying engines, you realize that a gain in one area will cause a loss in another.  High lift cams make it tough for engines to idle smoothly.  In this case you traded low-end drive ability for top-end power.  How was the car running before you installed all the go-fast goodies?  First off, you NEVER... EVER modify an engine that isn't running correctly.  This will make a nightmare for trouble shooting.  
 I doubt the exhaust leak would cause any real problem.  Chances are that your AFM (air flow meter) isn't calibrated correctly, your Idle Control Valve is dirty/bad, or your throttle position switch is out of adjustment/bad.  Also there is a Thermo-time switch on the thermostat housing.  This is really a sending unit, like the one that controls your temp guage.  This sensor tells the computer (ECU) when the engine is up to temperature.  When operating temp is reached the ECU will dial down the idle to normal range. This is most likely your problem.  You start the engine (cold) and it runs for a few minutes (5 based on what you said).  After 5 minutes the ECU is saying "Ok the engine is warm enough, lets lower the idle and run like normal".  Either this sensor is bad, or you dont have enough fuel getting to the cylinders.  
 The stock fuel system will only support up to about 170hp.  This is calculated by using the maximum volume of the injectors.  The M20 (your engine) makes about 165hp in stock form, so with a gain of 5hp you are already bumping the fuel threshold.  You have a cam, headers and probably a few other goodies that put you above this 5hp range.  In all likelyhood your engine will run out of fuel at high rpm, and run lean.  Running lean means high combustion temps and risk or ruining your engine.  Most guys that mod this engine buy the Ford 5.0L (302ci)19 pound (19#) injectors.  The 19# injectors are affordable, fit perfectly, and provide enough fuel for a modded M20.  
 On one last note, be careful with that camshaft.  I know several guys who race E30's with these engines, and most refuse to run aftermarket cams.  The problem is the rocker arms.  They are the weak link in the engine, and with high-lift cams they are known to snap easily.  
 Good luck, and have fun with the new engine!
 Josh