Silverunner

I just put a remanufactured engine in my 4runner 3.0 last weekend. Yesterday I drained the gas tank completely and put injector cleaner and 10 gal. of premium back into it. I drove it around town this afternoon with no problems. Around 80 miles on the new motor, it began to sputter when I accelerate. It also takes about 4-5 sec. to start everytime, but when it starts it idles fine? Any ideas as to why it started to sputter or why its hard to start?

Thanks
Steven