Home coach Peter Wright had been critical after his men had played well in fits and starts over recent weeks but yesterday, with Wright in Wales, his side showed what they are capable of when they compete for the full 80 minutes.
The hosts struck first when a kick ahead by Jordan Edmunds bounced perfectly for Craig Gossman. Chieftains struck back when Marc Kelly cashed over and Gregor Hunter converted, but the home side regained the lead when Greg Cannie darted in and Gavin Parker converted.
Thomas Gordon squared matters with a try from a close-range lineout and the visitors took the lead for the first time when Ben Robbins sprinted over, although, just before the interval, Parker cut the deficit to two points with a penalty.
Boroughmuir made a blistering start to the second period and quickfire converted tries by Jordan Edmunds and Will Wardlaw secured the bonus point and appeared to deflate Chieftains, who had no response to the relentless tide of green and blue.
Twice Boroughmuir were held up over the line before Johnny Matthews managed to breach the defence for try number five.
With the win secured, the next task was to deny Chieftains a four-try bonus. Not only did they achieve that, they also added gloss to the score when Matthews applied the final touch after a powerful surge by the home pack.
A bad day for Chieftains was exacerbated when they crossed the whitewash in the dying seconds but were judged to have knocked on.