Question on Boxster Common Engine Failures

I have purchased a 1999 Boxster 986 2.5 , seller had a dead battery and attempted to roll start car, the car done a major backfire he said, then he called for a jump start, car would only start backfire and cut off, he then removed engine cover and tops of left and right manifold are blown partially off, apart or separated at top, i have purchased used manifold set and going to install but i am wondering why backfire so strong that would blow manifolds, is there anything i should look for while manifold is off, i ran compression test drivers side front to rear cyl 1=160 psi, 2=180. 3=180 passenger side 4=175 5=180 6=135, all of which seem low but # 6 is really low , engine has check codes 115 mass air sensor. 112 hall effect sensor 1 and 113 hall effect sensor 2, i checked for water or signs of it in air filter and found none, i would hate to replace manifolds and blow them again, thanks

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This post was auto-generated based upon a question asked on our tech article page here: Pelican Technical Article: Common Boxster Engine Problems and Failures - 986 / 987

[Nick at Pelican Parts]

Your compression numbers indicate a faulty engine. I would perform a leak down test to find the course of the compression loss.

- Nick