To allow with the Map reading through with the Blacktop engine (see “load metering”) the inlet manifold features a wider confront for your side of the head with an additional vacuum feed off every cylinder that leads to an integral chamber for a vacuum sign to feed the Map sensor. https://donovanmomey.jiliblog.com/96114015/the-2-minute-rule-for-toyota-4age-blacktop-engine-for-sale