trouble codes

[traviS13]

can i still read the trouble codes on my car if a japanese tuning shop upped my boost i think with a chip but there was something to do with the blow off valve can you tune boost with a blow off valve. did i just make any sense. if not let me know ill try to be more clear. thanks oh yeah and what type of oil should i be using someone told me that the lowest weight should be 15w40 cause my car has added boost so at max boost 15 or 18 psi or something. its a ca18det so factory boost is around 7 or 9psi i think. someone else said nissan recomends 5w30 for the sr20det so im not sure if the ca18det would be different but anyways i was told 15w40 cause at high boost the low viscosity oil is too thin and will blow by valve seals or something. does this make any sense or have i been had. more thanks
Modified by traviS13 at 2:06 PM 4/11/2005

[s13sr20chris]

most chipped ecms can still pull up trouble codes(actually its all as far as i know). the ecm does not control boost. neither does the blow off valve. oil should depend on temp and of course you are turbo so go heavy. run a 10w40 or 15w50 in winter and a 20w50 in summer unless you see temp extremes.

[traviS13]

ok thanks for the help on the oil im glad i got that one ok and theres not an engine out there going to blow up cause of me. so then out of curiosity what controls boost levels. you can get boost controllers which are basically piggy back computers. so then your ecu would control your boost and the piggyback would lie to the ecu and fool it into making more boost. i could be completly off the mark please correct me if im wrong id like to know for sure.