Sorry, forgot to mention NGK BKR7E's need to be gapped to 0.80mm (32 thou). They came pre- gapped very close to this anyway.
On the mkiv.com site they recommend these plugs for the BPU upgrade and after doing a long search I found others on this site that also use them.
Got this from mkiv.com
Here is a list of the most commonly used spark plugs,
Stock Denso PK20R11, Comes pre-gaped at 0.043 inch (best on stock supra)
Stock NGK BKR6EP-11 (2978), Comes pre-gaped at 0.043 inch (best on stock supra)
NGK BKR7E (6097), Comes pre-gaped at 0.032 inch (best on BPU & APU supra)
NGK BCPR7ES (3330), Comes pre-gaped at 0.032 inch (best on BPU & APU supra)