My Roush experience was not all that pleasant but it was a 427IR (Fuel injection 8-stack). They had a total lack of understanding of that system. Customer service started off OK but when they finally figured out they didn't have the talent to do the correct work, they imploded and I basically gave up and went to a third party. Once the DFI system operated properly I had no issues with the engine. Mine did use a little
oil but nothing that I thought was excessive or more than normal for a high compression engine.