I had a MY99 & it would die at about 4,500rpm, turned out some peanut had added an extra olive to the boost line, ripped it out & it was fine after that, might be worth a look..........funnily enough it works great in my STI haha.

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Beaten up old 98 Gen 2 Liberty, 13.0, stock V3 STI running gear.
07 Transit motor home
69 VF & 70 VG Valiants needing full restoration
Yamaha Zooma 50cc rocket hopefully going with the Transit.