Going to play with the ignition timing some tomorrow. should i keep it in the range of 15-18 degrees?

Mods are DC header, Short ram intake, lightweight FW, and a test pipe.

 

15-16 will give you the most peak power, 17-18 will give you more power in the low-mid revvs.

 

The answer to your question really depends on what ecu you are running.
Changing your base ignition timing from 16 deg btdc at 800 rpms to 18 deg btdc at 800 rpms will change your whole ignition map's values.

I would honestly recommend leaving your ignition timing at 16.5 deg btdc (red line on crank pulley) & making the adjustments via a eprom editor using a chipped ecu such as crome etc.

For more info read http://phearable.net/tech/efibeginnerguide.html

 

I am running a chipped P28 tuned with hondata s300