Can a company have both a defined contribution plan, in which a participant contributes $40,000 a year (401k/PS plan) and also have a defined benefit plan (funding for the full 160,000) in the same year? In this case the DB plan is a 412i insurance funded DB plan.

I would appreciate your thoughts. Thanks.

Yes, but the employee can only contribute up to the 402(g) limit, i.e. $11,000, not $40,000. Anything beyond $11,000 (or $12,000 if a catchup provision applies) would need to be funded by the employer, and then you might run afoul of combined plan deduction limits. I don't know how a 412(i) limit would work, but for a normal plan the combined limit would be the greater of the amount required to fund the DB or 25% of aggregate eligible payroll. The fully insured arrangement may work the same, but I'm not sure of that.

Beginning in 2002, the employee deferral does not count towards the deduction limit, which makes a jumbo DB and a 401(k)-employee only combination feasible, and I doubt that there would be anything prohibiting the DB from being fully insured under this combination.