help with plugs

hi---i am a new owner of a 91 mr-2. engine is 2200 2.2. l. here is my problem and i need some help. car has 90K original and in great shape. has a set of bosch plugs fr7-dpx that need replacing (they are gapped at .020!!!). here is where the fun starts. book suggests bosch fr8-dpx (4002)---won't turn over when installed-factory set at .040 and i tweaked down to .020 and tried both--no luuck..old plugs back in works fine. then tried ngk size bkr5egp (7090). they worked great x 2 days then stpopped / fouled. check distance of plug base and it is identical to the old fr7's. bought bosch fr7's and went thru gapping and they worked great x 1 day then fouled. again, base is indentical to old fr7's. what is going on??? this is killing me.---thanks bob