swap gone wrong

[19peeps84]

hi folks, my problem is i had put my passat 1.8 20v n/a up for sale couple weeks ago but ended up getting offered a swap for a mk4 golf tdi.
So we met up on saturday and had a look at each others cars and done the swap as we were both pleases with what we saw, got home all happy with my golf, but wolk up on sunday morning with the other guy phoning me saying that he didnt actually own the golf as he got it off a so called mate but hadnt paid for it so his mate was still the legal owner as he still had the receipt for the car and wanted the money or the car back, even though the car was registered in the guy i swapped with name,
so he said he was coming through to my bit to swap cars back but what he didnt tell me was that he had knackered the engine in the passat and turned up at mine being towed by the AA and totally denied doing anything and just said the battery was dead, after a lot of hassle i had to let the golf go and get landed with a f**ked passat, he did say he would pay for any repairs that might be needed to the passat but funaly enough i havent been able to get hold of him since.
the battery is fine, there is fuel in it and getting fuel to the engine, im getting a spark, the engine will turn over but wont fire up, it just sounds different to it turning over normaly, i had noticed oil had sprayed up underneith the intake manifold so took it off to find a black plastic pipe next to the block had split so got my mate to turn engine over to have a look and almost like a backfire there was a bang, flash and big puff of smoke came out off the black pipe, im just hoping there aint a hole in my engine, im just looking for any ideas or help on this as i cant really afford a new engine and cant get a hold of the guy to pay for it either. many thanks