The gas insert might have been added because the chimney became unsafe to burn wood. Chimney inspection is necessary to look for cracks in the liner.

I will have that checked thank you

Short answer, "No". The tube was directly connected to the insert so all the gases escaped that way. Just leaving the tube in with non-vented gas logs would expel more gasses into the house than a flue without the tube. Your best bet is to stick with a gas or wood insert directly connected to the vent tube.

UnUnfortunately i really like the way the original fireplace looks and a dont want to use an insert. Is there a way to direct the gasses up the tube? something attached to the end that will direct them?

So, this is a brick chimney on an older house or are you saying that it was a zero clearance gas fireplace insert that has been removed from a newer home? If it is an old school brick chimney, it was built to burn logs and can burn gas too. If the old chimney was damaged and has cracks inside and someone might have thought an insert was cheaper than repairing. A crack in the old chimney lining can deliver fire into your attic space and is unsafe. If it was always a zero clearance fireplace and that insert has been removed then there is exposed wood framing up there and it is unsafe. Get a chimney inspection to find out what is what.

Old house with old wood burning fireplace that was converted to a enclosed gas insert. I dont know why the insert was removed. i want to use the old firplace with gas and cenent logs instead of a new insert.