rb26 is tuned with throttle for fuel. map for ignition.
there is not enough manifold to get the resoultion for a map only tune. eg. load rising can tune to a good 14:1 at a point but when lifting of or crusing at the same load point it could be 10:1 or 18:1.
i tried to change my tune to map only but just was not as good a a throttle/map configuration.
so to answer your question no you cant. and this is why the d-jetro is so hard to get correct. it may drive well and make good power. but put a wideband afr meter on it and it tells a differant story