My Blazer's high-rpm performance has really degraded lately. If I floor it in first, it revs but there's no giddy-up. No miss though. It idles fine, but also has a tip-in miss on slight hills. I had a mechanic check it and he said timing's fine, fuel pressure's fine. No codes. No lights. I had the cat and muffler replaced (flowmasters!), but it only helped low-rpm performance. It's a stock engine with 150k miles. Burns a quart about every 2k miles. I'm wondering ECU? rpm sensor? injectors? This a real head scratcher. I've got WinALDL and a home made cable, but can't seem to get it synced with the ECU. Any thoughts on any of these problems would be appreciated!