Difference between the BPR5 and BPR6 is how cold they run.
It may or may not make any difference at all. The most important difference in spark plugs is their gapping, which is usually either 0.8mm or 1.1mm, usually the old NGK system specified BPR5EY-8 or EY-11
Best I can find for an MA61 with 5M-E is chassis code MA61R-BLMQEQ
ToyoDIY.com
Denso to NGK apparently says the NGK equiv is BPR5EAL or BPR5EY (no mention of plug gap though)
I seem to think they need an 1.1mm gap though. Googling around agrees with this (I know this isn't the best way of answering it though)
I personally would not be worried if they were running BPR6's.
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