dbo.mytable a inner join dbo.mytable b on
a.tec_number = b.tec_number + 1 -- or -1, i'm not sure
datediff(mi, a.tec_insert_date, b.tec_insert_date) > 2
Note that this depends on tec_number being sequential with no missing entries (ie, a skipped entry may lead to invalid results).
The usual caveats about my code: it's usually ugly and slow.
Your mileage may vary, blindman will be along shortly to post the correct solution!