DES MOINES — Momentum for tax cuts is building at the Statehouse, but Iowa House Speaker Pat Grassley says his Republican caucus is maintaining a “cautious approach” until some unknown factors get resolved.First and possibly foremost among that list is how the COVID-19 pandemic has impacted Iowa’s economy and its ability to generate tax revenue — a question that could be answered as early as Friday when the state’s Revenue Estimating Conference meets to set revised projections for state tax collections over the next 15 months.The estimate will directly impact the outlook for spending priorities and tax reform policies.Currently, Iowa’s budget is in a surplus position with reserves full.