loss of power

i have an e30 325i with an e36 328i single vanos steel block engine with a dictator, it has a problem that when i turn on the lights it loses power, drops idling by about 200/300 rpm, it also doesnt want to turn off when the ignition is turned off for some reason, if anyone has any tips im open to trying them

Is this a new installation of Engine/ECU, or has the car worked previously, and this is a new problem? What ECU is being used? Have you looked at the idle control? Does the ECU have a way of detecting the additional load on the alternator?

Are there any mechanical issues (low compression, fouled spark plugs, dirty air and fuel filters, clogged injectors, etc).

As for not turning off - check the ignition switch, make sure the wiring isn't back-feeding some power into the ignition power circuitry. Have you modified the wiring recently?

its been working fine for about 2 months but it hasnt driven a whole lot, its only due for a service now, its running a dictator as a management system.

mechanically the car is fine besides being due a service.

ill give those things a look later today and get back

As David said - i would expect there to be a drop when different electrical loads are applied at idle, such as the heater fan, or engine cooling fan, as the alternator load will increase.

With it not turning off, I'd agree with the wiring most likely to be an issue. Even a bad ground can cause enough voltage to power the ECU/ignition - think of it as being like a bad tail-light ground, where the power to one filament can pass through the other to the other light's ground via it's filament.

how should i go about back testing it practically before plugging the laptop in, what would you guys recommend?

Use a voltmeter to test the ignition power fed to the ECU (I use back-probing pins if possibe, you could also pierce the wiring with a pin/needle). What is the voltage with the ignition switch off? What about when the engine is running? What about after you try to turn the ignition off while running?

Perhaps you have a bad ignition switch.