Hello all, been driving my 88 944s pretty heavily past couple days. Today it started making a sucking and ticking noise. Sucking sound I assume is related to a vacuum leak of some sort. Ticking isn't the valves, I've heard that sound and can tell the difference. I was wondering if it may be time for timing belt replacement. Odo stopped at 96k and haven't seen any documentation for the timing belt. I can post a video later but wanted to get a general consensus on what could potentially be wrong.
Thank you in advance

 

No document on the belt, you should probably do it anyways, and the rollers.