Certainly here /in the following link you/ confusion, both copies of the prototype I-307 or "FF" had two forced/reheated engine (plus armored cab and new brake wheel. The main differences of this modification.)
On through the basic MiG-9 were two versions with one engine - I-305 "FL" and the project I-320 "FN". Their scheme here: http://www.secretprojects.co.uk/forum/index.php/topic,6226.msg51380.html#msg51380
and the evolution of the MiG-9 from book - Alberto Trevisan "Storia ed Evoluzione dei Caccia Sovietici a Reazione,1945-1955"