Have a 99 TDI ALH 5 spd New Beetle. right at 300 k. Timing belt 50 k old. Has upgraded turbo at timing belt change ( a mild BW upgrade from kerma from their 150 hp package), also stage 2 clutch. upgraded map, new maf, kerma tune and Bosio DLC 1019 injectors. all tuned in. has run like a dream for the wife since done. out of the blue it lost power and started smoking like a toad. also was a bit hard starting and then real hard starting. I changed fuel filter, and also starter which fixed slow starting problem but not power and smoke issue. I know something is wrong even though it still scoots along and its STILL better than stock it is not even close to what it was capable of and the smoke is way increased under heavy foot. I noted my boost gauge will now peak at 15 to 16 psi whereas it used to spike to 23 -24 quickly and then level at about 20 when you really romped on it. it also seems to build boost slower. takes longer to hit 15 in other words. used to jump right up there. I have worked on it for some time now and am wondering how to narrow this down. I have VCDS. IQ is at 4.9ish. Injector timing is right at midline where it always has been since timing belt. verified today. again. On some of my hard 3rd /4th gear runs on hill I lose boost and have to cycle key to get it back. sometimes pops code when that happens but only for that. I noted a bit of a hose dilemma where the hose exits to turbo to intercooler and repaired that. need to upgrade to proper stuff but have not yet needs custom lines since no kits for new beetle with upgrades. sigh . it has run 50 k no problems but noted a small leak in line at exit. replaced hose with satisfactory temp one clamped down drove it no leaks there at least obvious ones and no improvement. intercooler looks ok no oil etc but not sure if that is good enough. very disappointing thought for sure that was it it really looks sound as far as boost lines are concerned after repair but not sure if the leak is happening when engine torques under load but shouldn't there be oil at leak site if that's happening? I guess my question is what does this sound like? how would you troubleshoot it? last time I took it to a shop in Ft worth that was allegedly reputable I got hosed by the sloppy job and insane prices for my prison shower repair job and really would prefer to look at this myself. I did the timing belt and the turbo and clutch and have had the front end off and on 50 times so pretty familiar with the cursed Beetle holding the blessed TDI and wish the wife would drive a jetta like me lol... any advice on how to procede would be greatly appreciated. will VCDS tell me anything? Requested and actual boost seem to match, IQ is ok, timing is ok? what if any data would help me narrow this down? not sure how to interpret N75 duty cycle In summary: what could be causing the boost to be a bit slow to climb, peg at 15-16 or so instead of usual 20' and it feel slower and spit smoke. also sometimes on my trouble shooting runs it suddenly chokes in 2nd gear rolling out of a slow turn and then suddenly comes on line again which has never happened before. Then it is consistently every time slower in 3rd upwards with the smoke, lower power and lower boost but only if you are romping on it going slow and easy it feels almost ok. should I just buy/make a boost leak checker and run it up to 20 psi or does this sound like it could be something else. the lines look good after repair. Also it is running hotter I am guessing egts are soaring with the heavy smoke and I am trying not to overdo it or damage it so limiting my test runs and letting it run easy afterwards... any advice on troubleshooting this efficiently would be appreciated.