Hi would switching to decaf be OK with IBS

Hi, bit embarrasing I have what I think is IBS, not sure, never had it diagnosed, anyway, I used to have the runs a lot, especially in social situations where I'd be nervous, anyway, I don't drink coffee any more and rarely drink tea because they are diuretics and with a bit of self confidence I don't seem to have the runs anywhere near as much as I used to, but the thing is, I really miss drinking tea, I had a couple of cups yesterday and it just went straight through me and the same today. If I switched to decaf, would it not have the same effect as regular tea? Or would it still set me off? And also, should I be eating more, or less fiber to prevent dirreah? I was thinking of maybe having a bowl of fiber based cereal everyday for a couple of weeks and see if it helps. Thanks in advance