88 is fine. If your basking spot is indeed 88 degrees and the ambient temps are correct, this is not the reason your snake is either vomiting or regurgitating.

There is a difference between vomiting and regurging. Regurgitation happens when the animal willfully stops the digestions process. Vomiting is involuntary and is more harmful to the snake for several reasons. Vomiting is not generally stress related and is caused by an actual medical issue.

Since your snake has regurged or vomited a couple of times, and you can probably safely rule our stress or temperature issues, you need to have him checked by a vet for an underlying illness.